Copper busbar, field width (- 5mm), suitable for busbar supports FST901N and FST903N. Width 1. Rated current (A) 1000 (852). Copper size L1 - 3 50 x 10mm. PU 1. Copper busbars. For 185mm busbar kits. Pre-assembled copper busbars in the sizes 30 x 10, 40 x 10, 50 x 10, 60 x 10mm in the following variants:. Horizontal design: - Field width. - Extended on one side (perforated from 20/30mm copper). - Extended on both sides (perforated from 20/30mm copper).