YONEX POLYTOUR REVIntroducing POLYTOUR REV! As a co polyester monofilament, this string will give you the needed control to execute your most powerful strokes. Packed with 8 sides, POLYTOUR REV not only puts a tight grip on the ball, it also comes with a SIF (Silicone Oil Infusion), which helps the strings snapback powerfully during impact for extra ball rotation. This co poly also has above average comfort for a poly based string, making it an obvious choice for any