ISOSPEED Black Fire 1.25 is a firm co-poly with exceptional control and surprising comfort. Given its low power, this one is perfect for advanced players who want maximum precision on their biggest swings. Given how fast this string allows the player to swing, the spin potential is excellent. Our TW playtesters reported a high level of pocketing, which is quite unique for such a firm control string. All in all this is perfect for the advanced baseliner looking for maximum control, durability and spin with above average comfort.