Scroll & Pinion Precision Machined and Hardened Should be Used With Back Plate (Adapter) To connect with Your Specific Lathe Spindle Outside Diameter: 5" Plain Back, Recessed 3.740" x 0.184" Deep Can Use Any Size 5C Collet From 1/16 through 1-1/8" Max. Accuracy: 0.0006 TIR Scroll and Pinion Design just like 3-Jaw Chuck, Operated With Chuck Kay.