Can be installed on Shimano A and Daiwa S size handle knob exchangeable compatible reels. Since it is a set of 2, it can be used for double handles, etc. Please check the manufacturer's website for detailed compatible models. Diameter 17mm, weight 5 grams. This is a used item, so there are some minor scratches, but it is clean. Each comes with service bearings, washers, and a spacer set. Instant purchase is welcome. Price negotiations and holds are "not allowed."