Our Pro Tru line of pistons utilize a plasma moly pre-gapped ring for the budget minded consumer. Wiseco Sport compact kits include the high quality NPR XX rings, which are the best quality steel nitrided top rings and napier style 2nd rings. Our late model EFI lineup and several small block Chevy pistons are designed around the our 1.2mm Steel Nitride and napier GFX rings. Many of our big blocks utilize a .043 back cut top ring for extra material thickness around the intake valve.FitmentYEARS MAKE MODEL ENGDESG NOTES1999-2010 SUBARU FORESTER EJ251;EJ253 16Valve; SOHC1999-2011 SUBARU IMPREZA EJ251;EJ253 16Valve; SOHC2000-2012 SUBARU LEGACY EJ251;EJ252;EJ253;EJ259 16Valve; SOHC2004-2012 SUBARU IMPREZA(WRX STI;WRX STI LIMITED;WRX STI SPECIAL EDITION) EJ257