The groundbreaking patented ratchet mechanism of the rotary circle cutter easily and efficiently cuts clean, perfect circles from 178" to 812" every time. Great for making circles for YoYo's, Cathedral Windows, Drunkard's Path, etc. Designed for both right and lefthanded use. Includes a builtin blade cover for safety, and a plastic guard to cover the pivot spike when not in use. Uses RB18 standard replacement blades.