Walton Plastics Engineering Rollover Vent Valves are manufactured to comply with the Australian Standard AS 2809.4-2001 Road tank vehicles for dangerous goods Part 4: Tankers for toxic and corrosive cargoes – Vent Valves Section 3.4.3 (b). They are built in PVC and chemical resistant products to prevent corrosion in service. Carefully engineered, these valves allow a vent of fumes but will minimise leakage in the event of a truck rollover.