? Constructed of alloy steel for long, durable service life ? Hardened to RC 52?56 to avoid damaging collet chuck threads ? Shiny taper with black oxide finish for the best combination of accuracy and durability ? Collet seat taper T.I.R. .0002 ? Collet face within .06 of nut face for maximum rigidity. ? Collet can be removed with single hand. No tooling required and improved collet life ? Precision ball bearing type collet races provide higher clamping forces ? Through-spindle coolant capability ? Parsymmetry design for high-speed operation ? Plastic bumper protects spindle and holder during tool changes. Available on NMTB 40 and 50 tapers only. ? Flange-entry coolant is the same as DIN Form B. Other sizes available on request