Eaton Weatherhead C3269X5X2 Carbon Steel Fitting, Adapter, 1/8" NPT Female x 5/16" O-Ring Boss Male (Pack of 4) Adapts 1/8" NPT female end to 5/16" O-ring boss male end Carbon steel for durability and resistance to rupture under high pressure For use with LP and natural gas, refrigeration, and hydraulic applications