Specifications: Brand: Tecnifibre String: Black Code 4S Gauge: 18 (1.20 mm) Type: medium stiff co-polyester string Comparable strings: Solinco Tour Bite Soft , Völkl Cyclone Tour and Diadem Solstice Power 17 Tested by: Name: Mike Playing strength: 4 /4 Player type: somewhat more classic player, flat groundstrokes, generates little spin himself. Had shoulder problems until recently Racket: Head Graphene Radical MP , 98 sq/inch, 16/19 stringing pattern String hardness: 24/24 kg with a stringing range of 22 -26 kilos Test duration: 5 hours 
Rating: Durability: 6 Tension retention: 8 Spin/slice: 8 Ball feel: 8 Power: 8 Control: 7 Comfort/arm friendliness: 8 Stringing the Tecnifibre Black Code 4S 18 was a walk in the park. The string (certainly this thin 18/1.20 version) is quite flexible for polyester standards. Despite the angled shape of the string, no problems at all with stringing. 
Review The first impression of the Tecnifibre Black Code 4S 18 was pleasant. The string offers a lot of ball feel and is not heavy on the arm. Given my shoulder problems in the past, the latter is very important to me. The grip on the ball for extra spin and slice was fine. This also gave the string some extra margin in my strokes. Although the string does not have the extreme ballbite of, for example, a Diadem Solstice Power 17 , it was more than adequate. The Tecnifibre Black Code 4S 18 also scored well in terms of tension retention . I experienced little loss of tension during the 5 hours of this playtest. I did find the string a bit 'jumpy', which did not always benefit ball control. However, I think that with the thicker 17/1.25 version of this string this is already a will be a lot less. I can't say much about the so-called 'rounding out' (losing the contour of the string after a few hours of playing), because after 5 hours of testing the string gave out. This low durability is also my only real negative point of the string. All in all, the Tecnifibre Black Code 4S 18 is a string with fine playing characteristics, but I found the lifespan limited compared to comparable strings with a 1.20 gauge.