This object is used to block the milling table for a 5 mm milling cutter. The outside diameter is 2 3/4 "(70mm). The diameter of the shoulder is 2 1/16" (52mm). The central diameter is 3/16 "(5mm). The object is fixed to the table by rotating it a few degrees. To extract it, position the tool in the 2 holes provided and turn in the opposite direction.