... PVC pipe, 3MM U-type galvanized steel shelves, closed-end regulator. Advantages: National standard material cages, good elasticity, deformation, ... , compression heat, deformation, not broken. Service life of 15 years. Ability to withstand compression: any adult can walk ... and healthy water. Useful life of 15 years.5Closed regulator: fully enclosed design, voltage regulator and filter with one, you can ...