This is the female version of the M2 Muzzle. The buckles are non-locking, and all straps have metal grommets and leather strap keepers, which is why the price is slightly higher.
Personally, I like the solidness of the metal eyelets when doing up the straps, and well as the extra weight and all the pretty shiny metal. But of course, locking has its distinct issues as well. It’s always hard to choose.
The cheek buckles are now available at the back of the head or forward.