A mouth plug is BDSM equipment that is used to gag the mouth. It comes in many shapes and sizes. It can be a ball that fits the mouth or a leather or rubberized strap that one bites onto. It can resemble a penis or a butt plug. A mouth plug limits a person's comfort and range of facial movements. It can increase a submissive's sense of vulnerability.
More About Mouth Plug
A mouth plug is not 'one-size, fits all' or 'one-type, suits all.' A person may feel comfortable with a certain size or type of mouth plug. Another may not feel the same way. Ill-suited mouth plugs can cause gagging and huge discomfort. So, it is important to select a fitting mouth plug first before engaging in BDSM sex play. Since the gear limits speech, agree on gestures that communicate discomfort.