The 4? Filter Replacement O-Ring Kit is for use with all 4″ Hi-Flow, Dry-Sump and Screw-On See Through Filter Assemblies. This Kit consists of three O-Rings. The smallest of the three fits into the sight window (O-Ring # V-153). The larger O-Ring fits into the filter top housing (O-Ring # V-154) and the largest O-Ring fits into the window retainer (O-Ring # V-155). All O-Rings are made of Viton? which is heat, chemical and fuel resistant. Recommended to install new O-Rings into See Through Filter when replacing the sight window in all 4? filter assemblies.