I've been through a few... A no name with attached halter (she got it off in about 30 seconds...) a 'horse' sized cribbing muzzle (metal bottom) with the rubber disc added to restrict grazing. Rubbed her like crazy, even though it didn't look tight and she wears a cob halter. Just bought the XL Best Friends muzzle that attaches to her halter (not the all in one). It's doing much better because we can keep the halter the right (cob) size but the diameter of the muzzle is bigger. I'm not sure how it'll hold up, as she likes to 'enlarge' the hole in the rubber piece, but I got it from Dover, so if she tears it up too fast, they'll let me exchange it!
Pisgah: 2000 AHHA (Holsteiner x TB) Mare (lower level eventing, with a focus on dressage)
Darcy: 7? year old Border Collie x Rottweiler? Drama Queen extraordinaire, rescued from the pound in Jan 2010
My percheron wears a draft size best friend all in one model. This is his 3rd season with it. You need to order the draft size directly from them, no one I know of carries them so I think they might be special order.