Two identical rackets that are not the same
Anyone who plays with two or more racquets of the same model knows this from experience: we tend to always reach for the same one in our bag. It's not a psychological issue—it's physics. Two identical racquets on paper can have different weight, balance, and swingweight, and our arm perceives these differences even when they're on the order of a few grams or a few points of inertia.
Matching is the process of adjusting two or more frames to match their measurable values, so that they perform equally well during play. It's a well-established practice in professional tennis and increasingly popular among advanced players seeking consistency between their rackets.
Why rackets don't come out of the factory the same
Tennis rackets are mass-produced, but the manufacturing process retains an almost artisanal quality. Strips of carbon fiber are cut, glued together, rolled around a mandrel, inserted into molds, and then fired in an autoclave. Each step introduces small variations: the amount of resin, the overlap of the fibers, the local thickness of the material.
The result is manufacturing tolerances that few manufacturers openly disclose. Depending on the manufacturer, the allowable variation in the weight of the bare frame can range from ±3 g to ±7 g. In practical terms, this means that two racquets taken from the same racket can differ by up to 14 grams in weight—and this difference translates into proportional variations in balance and swingweight.
For a player who uses just one racquet, this isn't a problem. For those who alternate between two or more racquets during a match or practice, the difference in frames translates into different arm feel, different swing timing, and inconsistent ball impact responses.
The Pro Stock world
Professional tennis players cannot afford such variability in their equipment. Their racquets—often called pro stock—are produced with select materials and to much tighter tolerances than retail frames available in stores. These are dedicated batches, not available to the public, and significantly more expensive.
But even with tight tolerances, matching remains necessary: the frames are measured individually and adjusted one by one until they reach identical values. On the professional circuit, a player can arrive on court with six or eight perfectly aligned racquets.
Those who play with retail racquets—the vast majority of players—start with wider variations between their frames, which makes matching even more relevant.
What aligns in matching
There are four fundamental parameters to work with in matching: weight, balance, swingweight, and twistweight. Not all of them have the same impact on feel on the court, and not all are equally easy to adjust.
The weight It's the most intuitive parameter: you can only add, never remove. The lightest frame is brought up to the weight of the heaviest by adding mass in the appropriate places.
The balancing indicates where the weight is concentrated along the frame. It is not an independent parameter: every gram added at a specific point simultaneously modifies weight, balance, and swingweight. It is this interdependence that makes matching an optimisation problem rather than a simple sum of weights.
The Swingweight It is the parameter that best describes the dynamic behaviour of the racket during the swing. Two rackets with the same weight can have very different swingweights depending on how that weight is distributed. It is the most important measurement to align to achieve a consistent feel between frames.
The Twistweight measures rotational resistance around the longitudinal axis and affects the stability of off-centre hits. It is mainly influenced by the weight positioned at the sides of the oval.
The challenge of matching is finding the combination of weights and positions that aligns all these parameters simultaneously—a calculation that, when done by hand, requires experience and numerous trials.
Where and how to add weight
There are essentially three positions where you can intervene on a frame: the handle, the stems and the oval.
The weight in the handle can be applied in two ways:
- The weight in cap It is the simplest to apply and remove. It adds mass to the lower part of the racket, increasing the overall weight without significantly affecting the swingweight. It is the ideal position when you want to add weight by moving the balance towards the handle.
- The weight on Handle, distributed under the grip, has a similar effect to a plug but with a more uniform distribution. It requires the dismantling and reassembly of the grip, which makes the operation less immediate but still reversible.
The weight on the’oval This is what has the biggest impact on swingweight and twistweight. The more weight is moved towards the head of the frame (12 o'clock), the greater the weight's contribution to the frame's inertia; weight positioned in the centre of the oval (3-9 o'clock) maximises the increase in twistweight, and therefore torsional stability. An intermediate position (2-10 o'clock) is generally the most balanced in the increase of swingweight and twistweight.
Weight in stalks This is what adds weight to the frame without affecting swingweight and balance. Adding weight in this area reduces the polarisation of the racket and gives a feeling of greater compactness and perceived weight.
The most common materials are lead adhesive strips and tungsten. Lead has the advantage of a density that allows for uniform distribution—one inch of strip (2.54 cm) weighs about 0.25 g—but it is toxic if ingested and requires care when handling. Tungsten is non-toxic but has more than double the density, which concentrates the same weight in a much smaller space. For the cork, a practical and completely reversible solution is to use a moldable adhesive paste such as Patafix.
The role of software in matching
Matching is a constrained optimization problem: weights must be added at specific positions to simultaneously achieve objectives on multiple interdependent parameters. It's the kind of problem that software can solve efficiently.
Inertia Racket Tuner is a free web app developed by Pagal Lab to assist with this phase of the process. Once you enter the data for the frames to be equalized—manually or by importing Inertia X1 measurement files—the app calculates where and how much weight to add, proposing concrete solutions with specific positions and masses.
The software manages the interdependence between the parameters: it knows that a gram added 60 cm from the handle has a different effect on the swingweight than a gram added to the cap, and balances the solutions accordingly. The user can choose the priority (prioritizing the swingweight or the weight), the type of weight distribution, and the maximum mass limits for each position.
Numerical matching and professional customization
An important distinction: numerical matching—bringing two racquets to the same measurable values—is only part of the work that can be done on a frame. Advanced customization, which modifies the playing characteristics based on the player's style, is a much more complex area.
Software makes calculations: it doesn't know the player's game, it doesn't know whether he attacks with a forehand or builds with a backhand, it doesn't have years of accumulated experience. A professional coach who has worked with a player for years can recommend changes that no algorithm can—he can tailor the racket to him. Software like Inertia RT can tell him where to place the weight to reach a numerical target; the right target for that player is indicated by someone who knows him as an athlete.
The purpose of the measurement tools and software is to make the player aware: to know what characterizes his racket, to understand where to intervene, and to be able to recognize a job done well — whatever path he decides to take.
To understand more about swingweight and why it is the most important parameter for understanding the dynamic behaviour of a racket, consult the article What is swingweight and why is it important to measure it.
To understand what twistweight is and how it affects the stability of off-centre shots, consult the article The twistweight: stability on off-center hits.
To try Inertia Racket Tuner for free, visit the pageInertia Racket Tuner.
