Boulderfly Rivet Removal Drill Tool Works with HSS or Cobalt Threaded Drill Bits (1/4"-28 threads) 3/32", 1/8", 5/32", and 3/16" Centering Collets 1/4" diameter chucking shank #40, #30, #21, and #10 Cobalt Threaded Drill Bits (2 1/8" length) are included