Inflatable gag
From wipipedia.org
An inflatable gag is a rubber balloon (often attached to a leather plate to hold it in place) with a valve and a pump. Once inserted into the subs mouth it is inflated to fill the subs mouth in much the same way as a ball gag. Inflatable gags are very effective in silencing the wearer but they also block the airway and for this reason the sub should never be left alone while wearing it.
