Plain Back 5C Collet Lathe Chuck Closer For Lathe Pinion Accuracy Machined and Hardened Should be Used With Back Plate (Adapter) To connect with Your Specific Lathe Spindle Plain Back, Recessed 3.740" x 0.184" Deep Can Use Any Size 5C Collet From 1/16 through 1-1/8 Scroll and Pinion Design just like 3-Jaw Chuck, Operated With Chuck Kay.