●Two-Piece Reversible Jaws; Jaws are composed of top and bottom pieces; American Standard Tongue and Groove Style; ISO3442 ●Highly durable; Steel inner mechanisms are quench hardened to increase toughness ●Plain back; Requires a fitted backing plate to mount to your lathes spindle; CME fully machined backing plates are available ●160 mm Chuck Diameter; 45 mm Through-Hole Diameter; 3 mm - 55 mm Clamping Range; 55 mm - 145 mm External Clamping Range ●130 mm Registration Recess Diameter; 5 mm Registration Recess Depth; Rear mounting bolt holes are positioned on a 142 mm diameter circle