Forge-welded treads, as per DIN 24351, made of grating with bearing bars 25/2, or 25/3, or 30/3 or 40/3, twisted cross bars and pitch 34x38mm, special side plates 70/3 mm with eyelets (to be screwed on the stair stringers) and anti-skid profile, hot-dip galvanized as per ISO 1461 (DIN 50976)