Perfect Circle® performance rings are the most extensive and technically advanced high performance rings in the industry. Driven by today's requirements for reduced oil consumption, lower friction, higher power output, and longer life, Perfect Circle is out front with the latest technology. Off the shelf sets, individual rings and custom finished rings are all available from Perfect Circle. The second compression ring on a piston contributes significantly to engine performance, particularly in racing applications. Unfortunately engine builders often overlook the importance of this ring when selecting a compression ring. Reverse torsional twist second rings have been the industry standard for many years, but offer only a limited performance advantage. If back pressure buildup from combustion gases leaking past the top ring is not controlled, it can cause the top ring to float, breaking the combustion seal and reducing power. This is why Perfect Circle® has introduced a new design in rings called the Tapered Hook Groove (THG) rings. These rings provide slightly better oil control than a reverse twist, taper-face ring, but most importantly, the new second ring acts as a check valve to relieve excessive combustion pressure build-up under the top ring, thus, stabilizing it and reducing the possibility of compression gases being trapped between the top and second ring.Pit Stop USA offers Perfect Circle File-Fit Performance Moly Piston Ring Set - 4.040" Bore 315-0005.045 at low everyday prices. Be sure to check out all of our products from Perfect Circle including Perfect Circle Plasma-Moly File Fit Piston Rings.