Koch Industries 4045221 PTO Quick Release Spline Adapter 21-6, Male Spline 1-3/8 by 21 and Female Spline 1-3/8 by 6 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 1-3/8 by 6 Adapter 21-6 Yellow zinc plated finish