Threaded couplings for suction or discharge of water or other fluids. Standard threading is NPSM+ADs- National Pipe Straight Mechanical. 1-1/2 and 2-1/2 are available with additional NST thread+ADs- American National Fire Hose Straight Thread. (NST does not interchange). Pin lugs are on all sizes of female end. 2-1/2 through 6 also have pin lugs on male end.