After testing numerous minute grind callouts, the final JP Enhanced Gas Rings spec is the perfect balance of a solid gas seal with a very low-friction relationship between rings and bolt carrier. Reducing the resistance between these components directly results in an overall increase in the rifle's reliability while the rings utilize the cycling action itself to scrape the walls of the carrier, helping shed fowling with every shot. The JPEGR-308 utilizes a one-piece design similar to the Mcfarland rings. Unlike the Mcfarland rings, though, our precision-ground gas rings are engineered to precisely suit DPMS-patterned carrier group components such as our own JP EnhancedBolt(TM) Mfg: J P Enterprises SPECS: Fits - DPMS LR-308 or AR15 rifles.