Never heard of them so did a quick search.......... Protects the stem from your teeth and vice versa. Here I thought it'd be like the finger condoms to keep saliva from spreading when someone gets slobbery sharing a joint or something
Google "silicone bong mouthpiece". The ones that look like ribbed butt plugs are pretty universal. The ribbed end fits most bongs and you can flip it over for the ones that it won't fit. And you can smoke joints with it too. They are good to to have if you go to pot lounges and smoke with strangers if you don't want to pick up all thier germs.