Bung mount mixers allow you to mount them directly to the 2” NPT bung on a 55 gal drum lid or on any other vessel. The folding props will slip through the bung opening and automatically open with centripetal force. The mixer will work both inside and center placed bung openings. With heat treated aluminum housing you get both outstanding durability and lightweight portability. All bung hole mixers come standard with a 5/8” diameter 316SS shaft and 304SS set screw attached impellers.