Koch Industries 4045143 PTO Spline Adapter 20-21, Male Spline 1-3/8 by 21 and Female Spline 1-3/4 by 20 Connect implements to a tractor's PTO shaft Allows for power to be transferred from the tractor to the implement Male Spline 1-3/8 by 21 and Female Spline 1-3/4 by 20 Adapter 20-21 Yellow zinc plated finish