Lifesystems Wetfire

The Wetfire Tinder Kit contains 8 Wetfire cubes for use with a foresteel, lighter or matches. The cubes are lightweight, non-toxic and can burn wet or dry.

Weight: 5g (each)
Dimensions: 30 x 25 x 25mm (each)

Wetfire burns even after 5 days submerged in water. I use the Wetfire in my own survival kit after seeing this.