This Is the 10 x 1.25mm Lite Lock from Harry B. Higley. FEATURES: Aluminum 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) Lite Lock