One that has:
1) Bee space on one side
2) Suitable sized gaps for workers to pass through
3) A frame rim properly sized for the hive
4) Near zero damage to the bees passing through
5) A self supporting non sagging design
6) Near zero possibility of propolis attachment to frame top bars
7) Durable
There is only one that meets those criteria, the wood framed Herzog (wire type)
The rest, without exception, are complete crap, thrown together by people that have never heard of LL Langstroth and who sell to fools who buy on price rather than quality, who then wonder why their hives are plastered with propolis and why the bees get pissed off when they ping off the QEx from the top bars.
plastic queen excluders
perforated steel queen excluders
unframed queen excluders