String Types: A Complete Guide

Choosing the right string type has a bigger impact on how a racquet plays than almost any other variable. The string bed is the part of the racquet that actually touches the ball, and its properties — elasticity, stiffness, texture, and durability — determine power, spin, feel, and arm friendliness.

The Five Main Types

1. Polyester (Co-Poly)

The dominant string on professional tours since the late 1990s. Most modern "poly" strings are co-polymers — blends of polyester with other materials to improve feel.

Properties:

• Stiffness: High (typically 200–300 N/mm string bed stiffness)
• Elasticity: Low — poly doesn't stretch much, so it returns less energy to the ball
• Tension maintenance: Poor — poly loses 20–40% of tension within the first few hours of play
• Durability: Excellent — rarely breaks before it goes "dead"
• Spin: High — the low elasticity allows strings to snap back rapidly, generating spin
• Arm friendliness: Poor for most players

Warning: Polyester strings go "dead" within 10–20 hours of play — the tension drops dramatically and the string stiffness increases. Playing with dead poly is one of the leading causes of tennis elbow. Restring frequently, even if the strings haven't broken.

Best for: Advanced players with fast swing speeds, spin-focused game styles, and healthy arms.

2. Multifilament

The closest alternative to natural gut in terms of feel and arm friendliness. Multifilament strings are made of hundreds or thousands of thin nylon fibres wrapped together.

Properties:

• Stiffness: Low (elastic, soft)
• Elasticity: High — stores and returns energy well
• Tension maintenance: Good — better than poly, not as good as natural gut
• Durability: Moderate — will break if you hit with heavy topspin
• Spin: Moderate
• Arm friendliness: Excellent

Best for: Players with arm problems, older players, beginners, players who prioritise comfort and feel.

3. Natural Gut

The oldest and still the best-performing string material in terms of tension maintenance, power, and feel. Made from the outer layer of cow or sheep intestine (not cat gut as commonly believed).

Properties:

• Stiffness: Low when fresh, maintains tension better than any synthetic
• Elasticity: Excellent — highest energy return of any string
• Tension maintenance: Best of all string types
• Durability: Moderate in dry conditions; poor when wet
• Spin: Moderate (less snap-back than poly)
• Arm friendliness: Excellent

Best for: Players with arm issues, players who want the best feel and power, hybrid setups (natural gut mains + poly crosses).

Tip: The classic hybrid — natural gut mains with polyester crosses — gives the best of both worlds: gut's power and arm comfort in the mains (which touch the ball most), poly's durability and spin in the crosses.

4. Synthetic Gut

A single-strand nylon string, sometimes with outer wraps. The "all-rounder" and budget option.

Properties:

• Stiffness: Medium
• Durability: Good
• Tension maintenance: Average
• Spin: Moderate
• Arm friendliness: Good
• Cost: Low

Best for: Recreational players, beginners, players on a budget who want a balanced string.

5. Hybrid Setups

A hybrid uses different strings in the mains and crosses. The mains (vertical strings) contact the ball directly and contribute more to feel and power. The crosses primarily affect durability and how the mains move.

Common hybrid combinations:

| Mains | Crosses | Effect | |---|---|---| | Natural Gut | Polyester | Max power + spin + arm comfort. Tour favourite. | | Natural Gut | Multifilament | Softest feel, max comfort. Great for arm issues. | | Polyester | Multifilament | Poly power/spin, softer feel than full poly. | | Polyester | Natural Gut | Uncommon — poly stiffness with gut durability in crosses. | | Multifilament | Synthetic Gut | Budget comfort setup. |

Quick Comparison

| Type | Power | Spin | Feel | Durability | Arm | |---|---|---|---|---|---| | Polyester | Low–Medium | High | Stiff | Excellent | Poor | | Multifilament | High | Medium | Soft | Moderate | Excellent | | Natural Gut | High | Medium | Excellent | Moderate | Excellent | | Synthetic Gut | Medium | Medium | OK | Good | Good |

Gauge (Thickness)

String gauge also matters. Thinner strings give more power and spin but break faster; thicker strings last longer but feel stiffer:

| Gauge | mm | Character | |---|---|---| | 15 | 1.41–1.49 | Thick, durable, stiff | | 15L | 1.33–1.41 | Slightly softer | | 16 | 1.26–1.34 | Most common gauge — balanced | | 16L | 1.22–1.30 | Popular with poly players | | 17 | 1.16–1.24 | Thin, more power/spin, less durable | | 18 | 1.06–1.16 | Very thin — mainly natural gut |