These valves are 100 percent effective and come ready to use. The 2x2x6 inch valves are reusable and can be trimmed for a custom fit. Easily mounted over bat entry holes and comes with mounting strap(not shown). It allows the bats to freely leave the building and when they return they won’t be able to get back in. Easy to use, comes with directions. Used by professional bat control specialists across the country. Eliminate bats from your house once and for all.