Bob Reeves 41sS 19 5.25 This is a Bob Reeves 41sS 19 5.25. Rim: 41 Cup: shallow-S Backbore: 19 Shank: #5.25 Purchased directly from Bob Reeves, Inc. in America. Because the cup is shallow, it's easy to produce high notes. Also, because the shank is #5.25, it goes in a little deeper. Therefore, even with a shallow cup and a 19 backbore, the resistance is slightly lighter, and you can play with a softer tone. Please consider it.