Steel Grating Stair Tread Ladder

We are offering steel grating stair tread ladder.
1) bearing bar (load bar) specifications (mm): the specification of plain type and serrated type bearing bar is 20 x 3 to 100 x 10; the specification of i-section type is 25 x 5 x 3, 32 x 5 x 3, 38 x 5 x 3, 40 x 5 x 3, 50 x 5 x 3, 50 x 7 x 4, 55 x 7 x 4, 60 x 7 x 4, 65 x 7 x 4, 70 x 7 x 4, 75 x 7 x 4, etc.
2) bearing bar pitch (center to center): 12.5, 15, 25, 30, 30.16, 32.5, 34, 40, 41.25, 45, 50, 60, 60.32, 80, 100 mm etc, also be according to client's requirement and 30, 40, 60mm are recommended,
3)america standard is available < 1'' x 3/16'', 1 1/4'' x 3/16'', 1-1/2'' x 3/16'', 1'' x 1/4'', 1-1/4'' x 1/4'', 1 1/2'' x 1/4''(19-w-4) and so on. >
4) material: mild steel (low carbon steel) or stainless steel
5) surface treatment: untreated, painting or hot dip galvanizing 6) steel grating standards: a) china: yb/t4001-1998 b) usa: ansi/naamm (mbg531-88) c) uk: bs4592-1987 d) australia: as1657-1985 e) japan: jjs.