B&B's Tapered Ring Compressors reduce assembly time and eliminate distortion and breakage of rings during assembly. Each ring compressor is precision machined from heat treated aluminum. The ID dimension is finished home to proper tolerance. The OD is machined with our exclusive Posi-Grip surface to prevent oily hand mishaps. We finish each ring compressor with a hard anodization to in-sure years of service. The only ring compressor for the professional ring compressor, precision machined from heat-treated aluminum and hard anodized. They feature a machine positive grip surface. Truly the professional way to install pistons.