I have one sized for backpacks and rollaboards. It works with my large waterproof duffle, as well.
They are a PITA to use, and have only used it a couple times. Once was to lock up my stich, boots, and tailbag--then put a cover over the bike. It worked very well for the purpose, but not something I would want to deal with for short stops.
Red hair and black leather, my favorite color scheme...