This is the Prop Nut for OS engines with a 1/4" crank thread. FEATURES: Metal Construction Black in color INCLUDES: One 1/4-28 Prop Nut REQUIRES: None, item is a stock part SPECS: Inner Thread Size: 1/4-28 Outer Nut Size: 10mm (.4"), use an 10mm nut driver if needed. Thickness: 5mm (.2") COMMENTS: This Prop Nut fits the following OS engines: -.25 LA -.25 FX -.32 SX -.40 & .46 LA series -.40 & .46 FX series -.46 VX -.50 SX series - FS-26 Surpass Four Stroke - FS-40 Surpass Four Stroke NNA 12/22/01