Do you mean crate FANS as in fans/lovers of crates?
If so, midwest icrate double door has always been a favorite of mine
(I like side doors, they can be pushed against walls and take up less space.) plus it folds down which is nice
Crate fans as in cooling fans for crates
I have yet to find one that works WELL.
This one from Dr. Foster & Smith at least works.
Nothing to write home about. It's plastic and the part that hangs on the crate isn't the best.. but hey, it works.
at the end of the day, the battery powered personal fans work the best, even through they don't hang from the door.