Safeguard Squirrel Controller one-way door, exclusion device. It measures 3.5"H x 3.5"W x 10"L and is made entirely of .5" x 1" mesh. Built with a spring-loaded door and 4 wings on one end which fits over the hole for easy mounting. Squirrels exit the structure and can't get back in. When the situation calls for it, or your customer demands exclusion versus trapping, these are a must.