Stop spills from going down the drain. Reinforced mesh is "sandwiched" between layers of polyurethane - increases durability and resistance to tearing. Unique, urethane construction allows the pad to deform and seal off most drains — temporarily "seals" to any smooth surface. A valuable addition to any emergency response plan, spill kit or stormwater management program. Unlike some alternative products, BOTH sides will quickly seal drains - there is no specified "top" or "bottom".