The ground-breaking patented ratchet mechanism of the rotary circle cutter easily and efficiently cuts clean, perfect circles from 1 7/8" to 8 1/2" every time. Designed for both right and left-handed use and reduces wrist fatigue connected with 'yo-yos', Cathedral Windows, Drunkard's Path, etc. Includes a built-in blade cover for safety, and a plastic guard to cover the pivot spike when not in use. Uses RB18 (standard) replacement blades. Guaranteed Forever.