These threaded adapter fittings are compatible with AN ORB (O-ring boss) ports. Because the threads on these fittings are not used for sealing, PTFE paste or thread sealant is not required. The O-ring should be lubricated with engine oil.
ORB ports are an industry standard and found on many automotive plumbing products, including most Radium products. All fittings include FKM (Viton) O-rings.