Engine Piston Ring Compressor Universal Includes Clamps and One Ring That Fits 3.875-4.375 Inch Bore Sizes ProformEasily install piston rings with the new PROFORM universal piston ring compressor installer. Kit includes one adjustable clamp that fits 3 7 8 to 4 3 8 inch bore sizes and one ring compressor. Just slide the clamp over the piston, tighten down to size, and tap into bore. It is that easy! Sold as one kit. Product Details: Engine Piston Ring Compressor Universal Model Includes Clamps and One Ring Compressor That Fits 3. 875 Inch To 4. 375 Inch Bore