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.
You can buy the Wetfire at grejfreak.dk or here:
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.