M12.5x12.4 – M Shapes

M12.5x12.4 is 12.5 in (318 mm) deep with a 3.75 in (95 mm) wide flange, and weighs 12.4 lb/ft (18.5 kg/m).

M shapes are doubly-symmetric, I-shaped sections that fall outside the standard W and S weight/depth series — typically lighter and often smaller than the lightest available W shape at a comparable depth. They're specified for light-frame construction, secondary framing members, and miscellaneous structural applications where a full W-shape section would be heavier than the load actually requires. Because the M series fills gaps the W and S series don't cover, it's a useful option whenever a project needs an economical, lightweight I-shaped member — mezzanine framing, light equipment platforms, and similar low-load structural work.