The string of choice for Stan Wawrinka, this durable co-poly string is very, very spin friendly. The slick surface of RPM Blast allows the main strings to slide out of alignment, grab the ball and then snap back to add spin to the shot. Though RPM Blast offers a slightly softer feel than traditional polyesters, it is by no means the softest co-poly available. It is an ideal choice for big hitters with heavier racquets seeking maximum control, durability, and spin.