33 CFR § 183.530 - Spud, pipe, and hose fitting configuration.
Except when used for a tank fill line, each spud, pipe, or hose fitting used with hose clamps must have:
(a) A bead;
(b) A flare; or
(c) A series of annular grooves or serrations no less than 0.015 inches deep, except a continuous helical thread, knurl, or groove.