This is the Cool Heavy Duty Head from Golden Horizons for use on the Traxxas 2.5 nitro engine.FEATURES: Aluminum Construction Two piece "button" style Removable top rim, anodized blue Five scallops cut into side of cylinder headINCLUDES: One complete cylinder headREQUIRES: Stock cylinder head mounting screws (TRAC2584)SPECS: Height: 49mm (1.93") Diameter: 42mm (1.7")Golden HorizonsPart GHH02208B