diameter 10

The adapter's function is evident directly from the manufacturer's data: it is used to connect bits with a 1/4" external hexagonal (hex) profile to tools with a 1/4" square drive

The product is an L-key with T-handle (hexagon) in a variant with internal hexagon 3

operating manual (documented)

Treston Electric Desk 1800x800 M1500 ESD for industrial use Unit(s):Pcs diameter 10Product Overview This electric sit stand desk from TRESTON, the Treston Electric Desk TED model TED818 49, is an electrically adjustable desk with ESD properties. The product is designed for industrial use and provides motorized height adjustment with direct up down control. Features Motorized height adjustment with up down control Semi conductive (ESD) laminated chipboard as tabletop Frame in epoxy powder coated steel, color RAL7035 (light grey)