With its grippy octagonal profile, this durable co-poly is very spin-friendly. The slick surface ofRPM Blastallows the main strings to slide out of alignment, grab the ball and then snap back to add explosive spin to the shot. While all co-poly monofilaments do this to some extent, our lab tests confirm that RPM Blast is exceptional in this regard. 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. (And it seems to be working quite well for Rafa!)