All States Ag Parts PTO Adapter Set Screw 1-3/8" 21 Spline Female 1-3/8" 6 Spline Male 125 HP 1-3/8" - 21 splline female x 1-3/8" - 6 spline male For tractors up to 125 h.p. Alloy steel, heat treated for extra strength Withstands high shock loads from tractor or implement Rust preventative finish