For securing large panels or tabletops in a way that allows them to expand or contract, due to changes in temperature or humidity. The screw slots prevent the wood from splitting and the screw from failing. Great for drilling and creating slots in one operation, #55230, diameter (D) 7/16, cutting Height (B) 13/16, shank (d) 1/2, overall length (L) 2-1/2, B1 1/2, Type Countersink, flutes 2, D1 11/64, 55230 Countersink screw slot 7/16 dia x 13/16 x 1/2 shank