The screw covers which are part of standard delivery can be plugged into the enclosure vertically or horizontally as required. The enclosure height (or width, if used vertically) can be extended by 15.24mm (3 HP) or 45.72mm (9 HP) by using extension sets. The boss dimensions conform – among others – to Euro card standards. Additional grooves for the insertion of circuit boards, mounting panels, etc., are located on the inner enclosure sides. 19" internal constructions for 3 and 6 U in widths 9, 12, 18, 21, 27, 30 and 36 TE are available on request.