This Is the 1/4 x 28 Prop Lock from Harry B Higley. FEATURES: Brass construction An electric starter or a backfire can cause the propeller to spin off especially with four-stroke engines. Any mechanic knows a second nut, screwed against the original one, locks both tightly in place. This Prop Lock replaces the propeller washer. A normal nut, or Heavy Hub is screwed against the Prop Lock. INCLUDES: (1) Prop Lock SPECS Shaft Size: 1/4-28 Diameter: 1" Thickness: 1/4" pjm 3/26/02 ir/kh kr3/27/03