This straight adapter joins an AN4 37-degree male flare to a 1/8″ NPT male pipe thread. The 1/8″ NPT port is the standard sender and gauge boss across a huge range of blocks, manifolds, filter heads and adapter plates, and pairing it with -4 AN hose is the usual way to run a remote oil pressure gauge, fuel pressure gauge or small turbo oil feed. The -4 AN side is deliberately modest in bore, which is exactly right for these low-volume, high-pressure duties. Apply a fluid-compatible sealant to the tapered pipe thread, kept a thread back from the leading edge, and assemble the flare clean and dry.