Used countersink stop for 1/4" threaded countersinks or drill bits. In good working condition.

Adjustable in approximate increments of .001" for precise counter-sinking. 
Accepts 1/4-28" threaded countersinks. 
5/8" cutter capacity. 
Rated for 3,000 RPM use.
Industry standard 1/4" chucking shank.