Spider gags are similar to ring gags, but they have a property that makes them more comfortable. The leather straps that are used to fasten the gag around the neck is attached to a metal frame that prevent them from putting pressure directly onto the cheek.
The ring makes the submissive drool and enables the dominant to insert certain objects into the mouth of the subject that is being trained. I personally like the aspect of drooling as it is embarrassing to the sub and uncontrollable.
This gag can be found over at De Tails Toys.