Oasis's feature is that it provides for a "wet" breath. There are 2 vanes near the demand valve lever that capture the moisture from your exhaled breath, on the inhalation- this breath passes over the deposited moisture and eliminates drymouth.
The Maximus is as described below in other post's. Practically every model from Sherwood/Genesis is bulletproof.
The Maximus is as described below in other post's. Practically every model from Sherwood/Genesis is bulletproof.