EXTRUDED FABRICATED ALUMINUM MATERIAL; 21 INCH BASE WIDTH; 4 FT HEIGHT TO TOP STEP; 4 HEIGHT TO TOP STEP IN FT; 300 LOAD RATING IN LB; 300 LB LOAD RATING; 30 INCH BASE SPREAD; APPLICABLE STANDARD ANSI A14.2, OSHA, UL; RATING TYPE IA EXTRA HEAVY DUTY