Rimba Bondage Play - Ribbed Urethral Plug This urethral plug has stimulating ridges that the user will feel when inserting the plug, providing an intense orgasm. The length of the plug is 242 mm. This item is available in two different thicknesses: Size 6 has a thickness that varies between 4.5 mm and 6 mm. Size 8 has a thickness that varies between 5.5 mm and 8 mm. Note: Always sterilize and clean the plug before use. To ensure smooth insertion, we recommend using lubricant.