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Tennis string knowledge in detail
Gut string
Natural gut strings are made from beef intestine – and are still considered the benchmark for elasticity, feel, and tension stability. The result: an extremely comfortable, arm-friendly setup with plenty of touch and a lively ball response.
The catch is clear: price & maintenance. That is why natural gut is usually for connoisseurs or ambitious players, and in the professional circuit, it is often played as a hybrid today – i.e., natural gut + synthetic string (e.g., for durability and more control).
Ideal for: Players looking for comfort, touch, and consistently high feedback.
Nylon strings
Classic nylon strings (polyamide) are the proven all-round classic: usually featuring a monofilament core and coatings that specifically influence the playing feel depending on the construction.
What makes them so popular: good elasticity, solid durability, and a very fair price. And the higher the quality/more complex the coatings, the closer modern nylon strings get to a multifilament feel (more comfort, more touch).
Who is it for?
Juniors & recreational players: uncomplicated, comfortable, reliable
Hybrid setups: great as a cross string if you want to optimize comfort and price/performance
Typical characteristics
Elastic → good acceleration / easy power
Arm-friendly → pleasantly dampened
Durable → robust in everyday play
Ideal for: recreational players & all-rounders looking for a reliable middle ground.
Monofilament (polyester) strings
Monofilament strings (polyester / co-poly) are the “performance class” of tennis strings. The string usually consists of a polyester strand with thin coatings. While the first poly strings were extremely durable, they often felt stiff and uncomfortable. That is precisely why co-polyester is found almost everywhere today: polyester with material additives for more feel, better feedback, and more modern playing characteristics.
What makes modern co-polys so exciting:
Many diameters (including very thin ones) → more feel & more spin potential
Many shapes/surfaces: round, angular, rough, twisted → targeted spin, control, or pop
Often, the orientation is already recognizable from the product name (spin/control/power) or via scales/points on the packaging.
Typical characteristics
Control & spin are usually the focus
The string notches before it breaks (visible notches)
Often surprisingly durable even in thinner gauges
Price: from budget to high-end – depending on the mix, coating, and processing.
Ideal for: modern baseline players with fast swings and a lot of spin.
Multifilament strings
Multifilament strings consist of many ultra-thin fibers, which are then encased in robust materials. The goal: to get as close as possible to the playing feel of natural gut – with plenty of comfort and a truly solid ball contact.
What you get in practice:
Very arm-friendly → pleasant if you are looking for comfort or are sensitive
High elasticity → noticeably easy power and good ball feel
When they wear out, multis usually do not snap “cleanly,” but rather fray (due to friction and the movement of the strings).
There are also clearly different orientations for multis (e.g., more power, more control, more durability) – you can usually identify this from the product name or the manufacturer scales on the packaging.
In terms of price, multifilament strings are in the mid-range, but are often slightly more expensive than monos.
Ideal for: All-rounders and players who want comfort & power.
Hybrid strings
We speak of a hybrid setup when you play with two different strings: one for the mains and one for the crosses. This is exciting when you want to specifically combine properties – instead of choosing “either or.”
The myRacket principle here:
The main property that you want to feel the most (e.g., spin) usually goes on the mains.
You complement the second property (e.g., power or comfort) via the crosses.
Typical hybrid combinations
Spin / Power
Power / Control
Spin / Control
The second major reason for a hybrid: greater durability – especially if you "eat through" strings. For this, people often rely on round or softer crosses to reduce friction and notch wear somewhat.
And yes: the possibilities are vast. Some manufacturers even sell pre-packaged hybrid sets. If you don't have any hybrid experience yet, a short consultation is worthwhile – then you will find the combination that really suits your game more quickly.
Ideal for: Players who want to combine the best of two string properties.
String gauge
Common string gauges generally range between 1.10 mm and 1.40 mm – which is why many strings are available in several thicknesses (same string, different feel).
You will often find the gauge rating alongside the mm measurement. Important: Gauge is "reversed" – the higher the gauge number, the thinner the string. However, manufacturers almost always print the exact mm value on the packaging as well.
Rule of thumb (myRacket logic):
Thinner = more playability (feel/spin/power)
Thicker = more durability (more robust, longer playing life)
The “sweet spot” for many players is in the middle at approx. 1.24 mm to 1.27 mm.
If your strings break too quickly, the simplest fix is often: go one gauge thicker.
Important note: Durability depends not only on the string itself, but also strongly on the racket – especially on:
String pattern (open = more movement/friction = tends to wear out faster)
Head size (larger = more string movement)
In concrete terms: With a large racket head and an open string pattern, it often makes sense to start directly with a slightly thicker string.
Also good to know:
The diameter specifications come from the manufacturer and are not standardized (they can vary slightly).
With angular/textured strings, the value depends on where it is measured (edge vs. surface) – which is why numbers can appear different depending on the measuring point.
Stringing intervals – when to restring?
- Casual players: every 10-15 weeks
- Team players: every 4–6 weeks
- Frequent players: significantly faster depending on wear
“Rule of thumb: Restring as many times per year as you play per week.”
String tension – the most important adjustment parameter
String tension is the amount of tension at which a string is strung.
It significantly influences the feel of the game – though differently than many people think.
What is actually true:
- Higher tension increases control because the string bed moves less
- Lower tension increases comfort and perceived power
- The actual ball speed changes only minimally – but the feel changes significantly
Practical play:
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High tension: more direct, more precise, small mistakes become immediately noticeable
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Low tension: more powerful, softer, larger sweet spot
Note:
The tension determines how strongly you perceive the material properties of the string – but it does not change the stiffness of the string.
String stiffness – the DNA of every string
The stiffness describes how much a string stretches upon contact with the ball.
It is a material property that is not changed by the stringing tension.
Physical relationships:
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High stiffness: short contact time, less energy absorption → more direct, more controlled
-
Low stiffness: longer contact time, higher energy absorption → more power, softer feel
In play, this means:
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Stiff string: precise, spin-friendly, but more demanding
-
Soft string: comfortable, powerful, but less control-oriented
myRacket-Insight:
A string is not "good" or "bad" – it must match your racket stiffness, your swing, your ball-striking quality, and your physical resilience.
Loss of tension – how long does your feeling last?
All strings lose tension – some of it immediately upon stringing and during the first few strokes.
After that, the rate of loss flattens out, but with every stroke, the string bed becomes a little softer.
What counts:
Not the pure percentage loss, but how the stiffness changes as a result.
The more stable the tension, the longer your racket stays the way you know it.
myRacket recommendation:
Frequent players should restring regularly, even if the string does not break.
Energy Return – Efficiency meets feel
Measures how efficiently a string transfers stored energy back to the ball.
However: high efficiency ≠ automatically more power.
Background:
- With stiff strings, more energy goes into ball compression (→ energy loss)
- With soft strings, more energy goes into string stretching (→ higher return)
In play:
Efficient, soft setups generate more “free power” and comfort.
Stiffer setups give you more precise feedback and more direct timing.
Spin potential – snap-back & grip
Spin potential depends on the ratio of frictional forces:
Spin potential = ball-string friction (grip) / string-to-string friction (lubricity)
Ideal:
High ball grip (rough surface or special coating)
Low string-to-string friction (mains slide easily & snap back)
The result:
➡️ Strings "snap back" after the shot, grip the ball more strongly and increase rotation.
Kirschbaum – strings that make physics tangible
More Power & Comfort
If you prefer to play the ball with an easy swing and are looking for soft, comfortable feedback, softer models like the Kirschbaum Touch Multifibre are perfect. It offers high energy return, minimal stiffness, and maximum ball acceleration – ideal for injury prevention and maximum comfort.
The Kirschbaum Synthetic Gut is also powerful: a classic all-rounder with balanced firmness and solid durability. Anyone looking for a blend of comfort and control will find an exciting solution in the Kirschbaum Gut Feeling Hybrid – a mix of polyester and multifilament that delivers power while remaining precise.
More Spin & Control
Do you want to dominate the ball and work with topspin? Then profiled and textured strings are your best choice. The Kirschbaum Black Shark 1.25 is a spin monster: its jagged surface increases friction on the ball, while the strings slide easily against each other – the perfect recipe for maximum snap-back and rotation.
For those wanting even more control and more stable tension, opt for the Kirschbaum Max Power Rough – a co-polyester string with high dynamic stiffness, a textured finish, and consistent playability even in tournament use. Slightly softer but with very stable feedback, the Kirschbaum Evolution is a
modern co-polyester mono that is particularly well-suited for fast, control-oriented players.
More Durability & Consistency
For frequent and tournament players, consistency is key. Strings like the Kirschbaum Pro Line II excel here, combining balanced stiffness with very low tension loss – keeping the feel consistent for weeks. The Kirschbaum Max Power performs even more precisely, losing almost no tension due to its high-modulus co-polyester and maintaining control even during aggressive baseline play. Those looking for a classic with a good power-control balance are on the right track with the Kirschbaum Super Smash Orange – a timeless all-round poly with robust performance.
myRacket recommendations – how to find your perfect string
If you are looking for more power and comfort, choose a string with low stiffness and high energy return. Soft multifilaments or hybrids generate more ball acceleration and are easier on the arm. Models like the Touch Multifibre or the Gut Feeling Hybrid are ideal for you – they transform every shot into clean, fluid power.
If you want spin and control at a tour level, you need strings with high spin potential – meaning a rough surface and low string-to-string friction. The Black Shark or Max Power Rough are built for this: they bite into the ball aggressively and snap back explosively after contact – perfect for aggressive topspin players.
If durability and consistent feel are more important to you than maximum spin, opt for smooth, tension-stable polyesters like the Pro Line II or the Max Power. These strings maintain their playing characteristics for a long time and are specially developed for tournament players and high-performance rackets.
And if you are simply looking for a balanced, reliable setup that harmoniously combines power, control, and spin, then the Kirschbaum Evolution is your key – a modern all-round poly that doesn't change your game, but completes it.