Plastic Excluders: Good for saving money, otherwise they suck. Flimsy,
cheap, you get what you pay for.
Wood Bound Excluders: Sturdy. The spacing of the wood encourages excess
burr comb which can be a clean up headache. However, the wood can be
notched with a router to provide ingress/egress for two queen management.
I keep a few around for this purpose.
Wire Bound: unless the notched entrance is desired, these are my
preference. Bee space is correct, they're sturdy and long lasting.
Aaron Morris - I think, therefore I bee!