Grating is designated by the bearing bar: depth first, then thickness. A 30x2.5 panel has bearing bars 30 mm deep and 2.5 mm thick. Depth is what carries load across a span, because stiffness rises with the cube of depth; thickness contributes far less to strength and far more to weight and cost.

That relationship is why a deeper, thinner bar is usually the efficient answer for a given load. A 40x3 panel is not simply stronger than a 30x2.5 one; it is stronger in a particular direction and heavier in a way that matters when the panel has to be lifted by hand for cleaning.

Bar pitch, the spacing between bearing bars, is the second number and it works against the first. Closer pitch adds strength and reduces the slot width; wider pitch drains better and uses less steel. The two together define the panel, and either alone tells you very little.

When you compare quotations, compare the sections rather than the descriptions. Two panels described identically in words can differ by 40 percent in steel weight, and the lighter one will be the one that deflects underfoot.