Our 40mm single-sided frame has a solid outside finish of smooth aluminum. The SEG extrusion is rigid because its backside has a longer metal edge for reinforcement, making it especially great for wall mounting and hanging overhead. Plus, it is lightweight. The silicone beading can fit 12mm. (.47 in) deep and 4 mm. (.15 in.) wide into the trough of the frame. Not compatible with lights (cannot be backlit).