Amazon.com: Tractor PTO Slip Clutch, 1-3/8" x 6 Spline (Both Ends) PTO Drive Line Accessory : Patio, Lawn & Garden
PTO Overload Clutch testing, servicing and calibration
How to remove PTO shaft from slip clutch on rotary cutter? - TractorByNet
Amazon.com : POWER PRODUCTS 3-Point Tiller Slip Clutch PTO Shaft for Rural King Country Way Sigma Rotary Tiller for ASC Rotary Tiller 77709 77710 77711 1-3/8×6 QR 1-3/8 RND 6 Spline Both
Weasler Universal Friction Clutch, 1-3/8 in. x 6-Spline at Tractor Supply Co.