This Little Giant Inner Cover provides extra ventilation and fresh air to your hive, as well as an extra layer of insulation and protection when placed under an outer cover. And by adding this wooden vented Inner Cover to your 10-frame hive, it prevents your outer cover from being propolized and stuck to the hive body. Made from 1/2″ plywood with tongue and groove framing. Fits on all Little Giant 10-frame Hives.