Pushing hard at the end of your ride, you might start getting that dreaded "Yama-thumb." It&&';;s crazy how that little blister on your thumb can make a day of riding a lot less fun. Sliding a donut to the inside of your grip will help alleviate that blister and make your session way better. Product Details Constructed from foam and Lycra Fits our grips, so should fit others as well 5mm worth of foam protection