1/4" x 28 UNF Floating Anchor Nuts. Anchor nut rivets to the underside panel using countersunk rivets, this creates a form of captive nut that is also self locking and strong. Also known as "Nut Plates" these handy little fasteners are great for removing panels and components quickly.
Pipe capacity of: 10mm (3/8"). Far exceeds Stauff pipe clamp specifications. Hydraulic part from the famous near £4 billion aircraft project. (Grounding strip present in bottom half of the clamp, see photos).