This straight adapter joins an AN4 37-degree male flare to a 1/4″ NPT male pipe thread. The two sizes are closely matched in bore, which makes this a tidy, low-restriction fitting for turbo oil feeds, oil pressure and fuel pressure gauge lines, small return circuits and vacuum or boost reference plumbing. The 1/4″ NPT port is extremely common on filter heads, blocks, manifolds and adapter plates. Seal the tapered pipe thread with a fluid-compatible sealant or PTFE tape wound in the tightening direction, kept a thread back from the leading edge so debris cannot enter the system. The AN flare seals metal-to-metal and needs nothing added.