3/8' od and yes flared..I have a #6 AN nut and plan altering block to take a screw in fitting.That way I can screw the dipstick tube to that fitting and seal off the leak that usually comes w/ original push in dipstick tube.You know how that syn
oil travels.I'll then bend tube to match original tube ,trim to length and have a bracke made and tigged to tube simular to original.