... , 60, 80, 90 mm etc. with 30, 40 mm recommended.Cross bar centers:any greater than 30mm is ok. with 50 ... -duty, well resistance of strong impact on surface. Gratings with cross bar centers at 50mm can bear lateral impact well. This ... . 2. Please provide complete design-related layout plan, structural drawing, sectional view and joint drawing. 3. In the case of stair treads ...