Straight fitting for any standard 1/4" BSPP port. Compression nut accepts standard 5/16" O.D. tubing. Compression fittings are designed to secure heavy-wall tubing using a bite-type ferrule and compression nut. These fittings accept our standard 5/16" O.D. tubing (cut off straight and deburred) as well as Fixture Hose and Heavy-Duty Hose with compression-type tube ends.