String comparison
RPM Blast vs Black Code 4S
Babolat RPM Blast against Tecnifibre Black Code 4S: ratings, specs and which one fits your junior.
The short answer
Both are polyester strings. RPM Blast leads on power. Black Code 4S leads on control, durability and tension hold. They score the same for arm friendliness (2/5). Black Code 4S costs less per set.
Ratings
Power
Spin
Control
Comfort
Durability
Tension hold
Ratings are on a 1–10 scale. The higher score is in bold when they differ.
Pick RPM Blast if…
- You want more power (6 vs 5 out of 10)
- Your player is younger (recommended from age 14 vs 15)
- Best for: heavy topspin players
- Best for: advanced juniors with fast, full swings
- Best for: players who generate their own power
Pick Black Code 4S if…
- You want more control (10 vs 9 out of 10)
- You want more durability (8 vs 7 out of 10)
- You want more tension hold (7 vs 5 out of 10)
- You want to spend less (from $14 vs $20 a set)
- Best for: maximum spin seekers
- Best for: advanced players with full swings
- Best for: control-obsessed baseliners
Specs side by side
| Spec | RPM Blast | Black Code 4S |
|---|---|---|
| Type | Polyester | Polyester |
| Construction | Octagonal high-density co-polyester monofilament | Square-shaped co-polyester with four spin edges |
| Gauges | 16, 17, 18 | 16, 17, 18 |
| Stiffness | Medium high | High |
| Set price | $20–21 | $14–18 |
| Reel price | $130–150 | $150–180 |
| Arm friendliness | 2/5 · Low | 2/5 · Low |
| Cost to maintain | 3/5 | 4/5 |
| Recommended from | Age 14 | Age 15 |
| Levels | Advanced, Elite | Advanced, Elite |
| Play styles | Baseliner, Big hitter | Baseliner, Big hitter |
| Junior tension | 46-50 lbs for juniors. String lower to unlock spin potential. Loses tension quickly so some players string 2-3 lbs higher. | 44-48 lbs for juniors. String low due to stiffness. |
RPM Blast in short
Babolat RPM Blast is one of the most iconic co-polyester strings ever made. When Rafael Nadal showed up at the 2010 Australian Open with this octagonally shaped co-poly, it changed the game. The octagonal structure with high-density co-polyester adds phenomenal rotation to the ball. The slick surface enables the strings to snap back with vicious force, resulting in extra RPMs. One of the most popular co-polys of all time, this firm and durable string is perfect for big hitters looking to load the ball with pace and spin.
Black Code 4S in short
Black Code 4S is Tecnifibre's maximum spin and control polyester with a square shape and four grippy edges. Lab tested stiffness of 209 lb/in makes it quite stiff. "This string's most undeniable characteristic was control" - it enabled playtesters to execute their most powerful strokes without fear of overhitting. The ability to take massive upward cuts combined with the four grippy edges was "a recipe for massive spin." Low powered but provides excellent bite on the ball.
RPM Blast vs Black Code 4S: quick answers
Which has more spin, RPM Blast or Black Code 4S?
They tie on our spin rating (10/10 each).
Which is more arm-friendly for a junior?
They score the same, 2/5. RPM Blast is recommended from age 14 and Black Code 4S from age 15.
Which lasts longer?
Tecnifibre Black Code 4S rates 8/10 for durability against 7/10.
Which is cheaper?
RPM Blast costs about $20–21 a set and Black Code 4S about $14–18, at typical retail.
The short answer and the "pick if" lists are generated from our ratings and junior data only. Data verified 2025-01 (RPM Blast) and 2025-01 (Black Code 4S).