I've been using a Muzzle Mate both at home and in the field since they first came out. Wish I had a source for the clear plastic tube though, as it discolors and gets a bit knarly after a few years of use from contact with bore solvent. Mine came from Sportsman Whs.
But here's another upside to these things, on more than a few occasions when in the rat patch having our way with Skippy and his pals, the landowner has come by our shooting setup and commented that they appreciate us catching all the used, dirty patches and not leaving them laying about on the ground. A good rapport with the guys who provide the land and rodents for us is a very good thing.