Specification - P6230 - Heavy Duty 3in Wide Stainless Steel Trench Grate MIFAB series P6230 - 3in wide heavy duty slotted trench grate constructed of 10 guage, Type 304 stainless steel with 1in x 1-3/16in stainless steel angle frame. Free area of 20 square inches per 3ft section. Standard with ANSI rated "Heavy Duty" slotted Type 304 stainless steel grates with a load rating of 5,000 to 7,000 lbs.