Flat Contact 0. S4 SRA White Heavy Duty Food Grade Safety Wellington AntiSlip and Antistatic Conforms to BS EN ISO 203452011 S4 SRA Steel Toecap ST91100. Mid Cut Safety Shoe with Shoe Lace Cw Steel Toe Cap with. Diagram 1 2 refers to footwear with different design in terms of height and parts. Many countries have established their own specifications of safety footwear.