Just had someone try to ship me a couple of 5" madtom catfish in Kordon breather bags. Poor little guys poked holes in the bags with their pectoral fins. They might have been okay in another situation, since they were still wet, but the bags plastered against their faces and covered their gills. Result: Two DOA madtoms. They were about 5" long, so they weren't even very big, but I guess they wiggled too much.