The Tunneler's Friend is a two-mode seal intended to provide an air supply to its user.

Accumulates up to 300 air points over the course of an hour in Mode A. Releases up to 300 air points in Mode B. One person at rest uses up 1 air point per minute. Light exercise (e.g. walking) uses up 5 air points per minute. Moderate exercise (e.g. hiking) uses up 20. Combat uses up 50.