tecnifibre 4s 200m rulle 1Black Code is Tecnifibre's best selling polyester tennis string. The 4S was formerly known as the Black Code 4S but now goes by the name 4S only. Like Black Code, 4S provides good control but generates even more spin than Black Code due to its 4 edge structure and it is both softer and holds pressure longer than comparable strings on the market. Durability: very high Playability: high energy on returns Arm friendliness: medium absorption of vibrations