They look very similar to the cobette waterer that fills with slime. They also have a flap the animal would have to push down in order if them to drink. I don't think the deer are going to push that big flap. There is no moving parts on the Jug waterer for the animal to push or ware out/rust. The jug Waterers are used by lots of deer farmers for several reasons. They are dependable, they don't freeze up, they keep the water cool in the summer, and they are algae free! What more would you want in a waterer. Buy one and give it a try and I'll bet you will be buying more.