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A universal string tensioner

Elevate your game

All tennis strings experience rapid tension loss, this has a huge impact on your game. Keep your strings longer tensioned with the Retenser.

  • Extended playing comfort

    Experience more relaxed and controlled swings and achieve more power.

  • Easy and timesaving

    Reduce the hassle around restringing your racket often with our easy-to-use system.

  • Re-usable and affordable

    Our innovative technology can be re-used multiple stringing jobs. 

    Learn more about the Retenser story .

    How it works

    Keep your tennis string longer tightend in a single, easy hand movement using the adjustable string tensioner that fits all tennis rackets.


    The Retenser is easily installed on your racket bridge during stringing.


    Tension is adjusted by rotating the cylinders with the key provided.


    • Start

    • Middle

    • Plus

    You can add tension twice before it’s time for your next restring.


    The Retenser can be used for multiple stringing jobs, it’s re-usable.

    ITF approved


    Upgrade your game with Retenser and experience unmatched control, lots of fun and save precious time on restringing.

    Retenser Standard

    The Retenser standard is for every tennis player at every level. It includes 1 set of cylinders (medium).

    Retenser Standard

    24,75 euro / excl. shipping, tax & duty

    The Retenser standard is for every tennis player at every level. It includes 1 set of cylinders (medium).

    Retenser Pro

    The Retenser PRO is for the more material conscious tennis player. It includes 3 sets of cylinders (soft, medium, hard).

    Retenser Pro

    33,02 euro / excl. shipping, tax & duty

    The Retenser PRO is for the more material conscious tennis player. It includes 3 sets of cylinders (soft, medium, hard).

    What other people say about the Retenser


    A simple question from a tennis coach led to the development of an award-winning solution for tennis players

    Every string naturally loses tension over time, regardless of whether you play or not. This fact led to Sander van Heijst’s development of the Retenser. He personally witnessed the equipment’s impact on his tennis game during his professional international tennis career.

    Sander has been a tennis coach for over 25 years, often recommending that tennis players replace their strings. Lack of time is a commonly cited counterargument. Consequently, many tennis players continue to use old strings for too long. Sander pondered why it’s possible to instantly tune a guitar but not a tennis racket. This question inspired Sander to create the Retenser. He built the initial prototype himself and was very satisfied with its impact on string tension. Subsequently, he collaborated with a design agency to further develop various prototypes, leading to the creation of the Retenser


    Read our FAQs to get a comprehensive understanding of how the Retenser can transform your game.


    I have received the Retenser at home, what now?

    Upon receiving your Retenser, the next step is the installation on the bridge of your racket. If you’re familiar with stringing, you can do it yourself, look at the installation section of this FAQ. Here you’ll find detailed instructions and two helpful installation videos. However, if you’re not comfortable doing the installation yourself, there’s no need to worry. Simply visit your local sports shop or consult the stringer at your tennis club or your tennis coach. Show the installation video which is conveniently accessible via a QR code and they will know what to do. Remember: the Retenser installation always comes with a new string.

    What does the Retenser do?

    String tension naturally diminishes over time, whether you’re actively playing or not. With the Retenser, you can restore and tighten your string tension, revitalizing the feel of your racket to that of a newly strung racket.

    In addition, it may be desirable to adjust the tension of the racket in changing circumstances:

    • When facing an aggressive opponent on a fast surface like artificial grass, you may seek better control. The Retenser allows you to boost string tension, significantly enhancing your control and precision on the court
    • On slower surfaces such as clay, in damp conditions, or when energy levels are lower, the Retenser offers the flexibility to play with reduced string tension. This adjustment creates a more pronounced trampoline effect, allowing you to hit the ball deeper with the same effort.

    A simple adjustment with the Retenser will give you a noticeable change in performance.

    Does the Retenser work on every type string?

    Yes, the Retenser can be used with any type of string.

    Does the Retenser help reduce the risk of injuries?

    When discomfort sets in, a common response is to unconsciously tense up, leading tennis players to grip their rackets more tightly. By maintaining proper string tension, the ball comes off your racket more clearly, providing a positive impact both mentally and physically. This promotes relaxation during your swing, reducing unnecessary muscle tension and could contribute to lowering the risk of injuries.

    Why are there two versions (2 or 3 cylinders) of the Retenser?
    • The 2-cylinder Retenser is designed for rackets with 4 loops in the bridge.
    • The 3-cylinder Retenser is designed for rackets with 3 loops in the bridge.
    What are the benefits of the Retenser Pro?

    The Retenser Pro comes with three cylinder options:

    • Soft (blue cylinders) in two steps 0.5 kg, total 1 kg. 
    • Medium (white cylinders) in two steps 1 kg, total 2 kg.
    • Hard (orange cylinders) in two steps 1.5 kg, total 3 kg.

    This extensive range enables you to more accurately apply your desired tension.

    Additionally, the Retenser Pro package includes a second adjustment key and a convenient storage pouch for the spare cylinders, providing greater flexibility and convenience.

    Does the Retenser have an impact on my racket’s weight and balance?

    Adding a Retenser results in a negligible increase in weight, barely noticeable. It’s important to note that any alteration to a racket’s weight has an impact. On one hand, the Retenser contributes to added weight, while on the other hand, it replaces the grommet strip at the bottom of the bridge, which offsets weight in the same area. The overall effect is an increase of approximately 5 grams. For reference, racket weights typically range between 250 and 320 grams, making this weight gain typically less than 2%.

    The Retenser is installed on the bridge, precisely in the middle of the racket, both along the horizontal line (from head to handle) and the vertical line (from left to right side of the head). This means that it minimally disturbs the racket’s balance.

    Is the Retenser patented?

    The Retenser is protected by patents in the European Union, in the U.S. and elsewhere for Elevating Sports BV. This virtual patent marking notice is provided to satisfy the virtual patent marking provisions of various jurisdictions including the virtual patent marking provisions of the America Invents Act and provide notice under 35 U.S.C. §287(a). The following list of products and patents may not be all inclusive.

    Products Name:

    • Retenser 2 cylinders version
    • Retenser 3 cylinders version
    • Retenser Pro 2 cylinders version
    • Retenser Pro 3 cylinders version

    Patents/published applications:

    • EP 3974037 A1
    • US 2022/0088444 A1
    What is the Red Dot Award?

    Each year, the Red Dot Award celebrates the most outstanding and innovative products from around the globe. These products are distinguished by their captivating aesthetics, functional excellence, intelligence, and groundbreaking innovation. What unites these award-winners is their exceptional design quality. We take great pride in announcing that the Retenser received the esteemed Red Dot Design Award in 2021!

    The Retenser, featuring the CCT (Conic Cylinder Technology) mechanism, developed and patented by us, clinched the title in the “Most Innovative Sport Product” category. 

    Will my Retenser fit if I buy a new racket?

    Compatibility with your new racket depends on the number of strings in the bridge (the curved part at the bottom of the racket). If your new racket has the same number of strings in the bridge, your existing Retenser will also fit the new racket. However, if the string count is different, you’ll need a different Retenser type.

    Please be aware that the bridge’s shape on the new racket may vary slightly from your current one; some models are flatter, while others are more rounded. The Retenser is supplied with two ‘base parts’ – one slightly flatter and the other slightly rounder. Both ‘base parts’ are made from a flexible material that adapts to the bridge’s shape. In this way, the Retenser will still fit, but you may require the alternate base for your new racket. It’s advisable to store this extra base securely upon purchase.

    How does using a Retenser affect string lifespan?

    By allowing you to maintain string tension with precision, it enhances the quality of your string, ensuring you get the most out of your purchase.

    Can the Retenser cause racket deformation?

    Racket deformation is a natural occurrence when transitioning from an unstrung to a strung state. Any strung racket, over time, will experience some degree of movement due to tension loss. To mitigate this, we recommend tensioning your racket at a maximum of 24 kilograms. This ensures that the total kilogram force, even after adjustments, remains within the standard safety margins for tennis rackets, even when using the orange cylinder (maximum 3 kilograms).


    How do I install the Retenser?

    The Retenser can be installed by every stringer. If your stringer is not already familiar with the Retenser, show the installation video and they will know what to do. If you or your stinger have any questions, please contact us via We are always here to help.

    Is the Retenser compatible with all tennis rackets?

    Each racket model has a slightly distinct shape for the bridge (the curved bottom of the racket). The Retenser package includes two ‘base parts’ to accommodate these variations: one with a slightly flatter shape and the other slightly rounder. Both ‘base parts’ are crafted from a flexible material that adapts to the bridge’s shape. Consequently, the Retenser is designed to fit on nearly all modern rackets.

    Where is the Retenser installed?

    The Retenser is attached to the racket’s bridge (the curved portion at the racket’s base) during the string replacement process.

    Can I install the Retenser on my own?

    For those familiar with stringing tennis rackets, installing the Retenser is a straightforward process, requiring minimal extra time. You can refer to instructional videos for guidance.

    Which position to install the Retenser?

    We advise utilizing the Retenser in the “minus position.” This allows you to make two tension adjustments: from the minus position to the middle position and from the middle position to the plus position. It’s crucial to ensure all cylinders are set in the same position.

    Must all the cylinders be in the same position?

    Yes, because otherwise you will get uneven tensions in your racket.


    How to adjust the Retenser

    Easily customize your string tension with a simple hand movement using the included key.

    Please take note: When making adjustments, be sure to maintain a firm grip on the adjustment key. String tension can exert significant force on the strings. We recommend sliding your finger through the cord to secure the adjustment key and prevent any accidental slips. Your safety and precise tension control matter to us.

    Why are only the longitudinal strings tightened?

    The main strings have the greatest impact on the tennis game. Because the strings are woven in, you experience the feeling that your entire string bed has been tensioned again.

    How often can I re-use the Retenser

    The Retenser is made of very strong material that is capable of resisting great forces. This makes the Retenser last a very long time and can be re-installed multiple times.

    How do I know when the Retenser is no longer functioning?

    When the Retenser no longer clicks into the desired position and consistently overshoots, it’s time to consider getting a new one

    Can I order the adjustment key separately?

    The Retenser Standard comes with one adjustment key, while the Retenser Pro includes two. We do not offer individual component sales, including keys. Our adjustment keys are equipped with cords for easy attachment to bags, clothing, keys, and more, to minimize the risk of loss.

    Is the Retenser allowed in competitions or tournaments?

    The Retenser is officially approved by the International Tennis Federation (ITF), making it eligible for use in all professional matches.


    How do I know when it’s time to replace my string?

    You should consider replacing your string when you notice that strings crack, fray, fail to snap back into position and when strings are misalign. 

    Why choose a Retenser and not just a new string?

    Opting for the Retenser allows you to easily maintain string tension, saving time and effort. To achieve a similar effect by frequently replacing your strings without the Retenser, you’d need to restring your racket multiple times within a season.

    When does my string looses tension?

    Once a tennis string is removed from the stringing machine, it immediately loses tension. This tension loss is further affected by factors such as gameplay, non-usage, temperature, storage conditions, playing style (e.g., powerful shots, topspin), and more. While you can continue to play with a string even as it deteriorates, it will progressively impact your physical, mental, and technical abilities, ultimately affecting your game and overall performance.

    What are the noticeable effects of tension loss?

    As the game progresses, you might observe a diminished response from your strings and racket. This necessitates increased effort on your part to generate power, making it necessary to exert more force in your shots, especially for hitting deeper or targeting specific areas on the court. This added effort can potentially compromise your hitting technique. Furthermore, the mental and physical demands rise, potentially reducing your enjoyment of the game. Increased reliance on your own strength also heightens the risk of physical discomfort.

    Does the sweet spot stay the same?

    Once the Retenser is attached to your racket, the strings extend beyond what they would in a racket without it. This happens because the strings are threaded through the Retenser. Consequently, the sweet spot immediately expands upon installation of the Retenser. This enhancement offers the benefit of delivering more powerful and precise shots with the same level of effort.


    Our customer service team is here to assist you and your stringer. Please do not hesitate to reach out to us at We are always ready to provide support.