Rather than relying on the piston skirt to locate the pistons as they're being inserted into the block like one-piece tapered ring compressors currently on the market, the new BTR ring compressors have a small but very important reverse chamfer at the bottom that fits into the chamfer at the top of the block which serves two functions.

Size: 3.780"
Brand: BTR Brian Tooley Racing
Type: Piston Ring Compressor Installation Tool
Manufacturer Part Number: BTR RC
Country/Region of Manufacture: United States
Unit Quantity: 3.780 3.800 4.000 4.005 4.065 4.070 4.125 4.130