The Unistrut cantilever arm is a heavy-duty 2.5mm thick stainless steel 41mm wide channel. The arm length is 300mm and the base dimensions are 135mm x 45mm. It has two 14mm holes for mounting. Note: Material thickness for all channel types is 2.5mm, and internal slot width is 22mm for the galvanised steel channels and 21mm for stainless steel types.