One size fits all 8 and 10 frame hives. Easy to switch from 3/8'' to ¾'' with our telescoping metal slider. Eight 3/8'' entrance holes. Made with durable 24 gauge baked-on white metal. Screw holes provided if you want to fasten to hive. Mouse-proof. Hive not included. Comes in a package of 10 Entrance Reducers.