This bit is designed especially for cutting fiberglass, fiberglass PCB board, composites, phenolic and other highly abrasive materials. Works well on epoxies made with carbon, glass and composite Materials. The Up-cut/down-cut diamond pattern cutting edges effectively grinds through the material evenly in all directions, #46099, diameter (D) 1/4, cutting height (B) 3/4, shank (D) 1/4, overall length (L) 2, type ultra-fine, style end mill point, end mill point diamond pattern composite cutting 1/4 dia x 3/4 x 1/4 inch shank