This shim can be used to provide upper entrances for your bees during the honey flow. This provides extra ventilation and can help alleviate congestion in the brood boxes. The shim must be used with honey boxes full of drawn foundation. This device can also provide added space when using mite control products such as ApiGuard. Talk to us in the shop for more details on how to use shims in your hive. Fully assembled, made in Corvallis. Choose 8 frame or 10 frame size.