A tunnel plug is a hollow anal plug whose opening is the feature. Once worn, it leaves a round window. People use that window for looking, for adding a slimmer toy, or for the particular stretch of a thick wall with an empty core.

The inner lip should be rounded on both faces. A square inner edge becomes a blade when something moves through it. Steel tunnels hold a perfect circle. Silicone tunnels feel warmer and can oval under clench, which changes the usable bore.

Anything passing through should be narrower than the opening looks. Eyesight is optimistic. Lube the inner lip as well as the outer bulb. Clean the bore with a brush; a finger does not finish the job.

Limits

• Do not treat the tunnel as a challenge for the largest second toy you own.
• Remove if the rim goes numb.
• A wide outer flare is still required.
• Skip long wear until short wear is easy.