With polyester strings continuing to dominate the stringing spotlight, it's no surprise that string manufacturers are continuously innovating and releasing new polyester strings designed to provide more spin, better tension maintenance, and improved feel.  French string manufacturer Tecnifibre jumped back into the fray with Black Code 4S, a new take on their Black Code poly that features a square profile and is designed to provide maximum spin, power, and durability, all while offering excellent tension maintenance.

Installing Black Code 4S was actually a lot less trouble than expected.  Typically geometric or textured polys can be a bear for the fingers, but 4S wasn't terribly onerous even though the edges were definitely noticeable.  Coil memory seemed typical for a polyester but, with a little care, tangles and kinks were easily avoided.  As with most geometric or textured polys, installing crosses comes with some risk of damage due to the sharp edges.  I didn't have any issues, but I'd still encourage other stringers to take their time installing crosses—especially if they're blending Black Code 4S with another, softer string.

Once I got to the courts, 4S was about what I expected from a geometric poly—spin potential was above average and feel was solid, though not as crisp as I typically like.  The flipside is that 4S felt very soft and was one of the most comfortable polys I've used in quite a while.  Fortunately, the soft feel didn't come at the expense of durability.  I played past the 12-hour mark with my set and didn't break it, though they definitely felt a little dead towards the end.  As I've noted in the past, I find that most polyester strings go dead and lose tension well before they snap, though I'd expect that heavy string breakers may break Black Code 4S before it goes dead or gets mushy.

Overall, I'd say that Black Code 4S is another solid entry into the premium polyester category.  It's not a totally novel string, but it's certainly above average—especially in terms of spin potential, comfort, and shock absorption.  Give this one a shot if you like polyester and maximum spin, but want something easier on the arm.