Usually those tinders are a sawdust and parrafin wax compressed cake. They do take a bit more effort to ignite. If you want to carry a small tinder directly in a PSK they work well. I like vaseline and cotton balls because #1 you can stuff a good quantity into various small containers ( 35mm film canisters, ziplocks etc.) #2 it's inexpensive to make up a supply #3 you can play with it under various conditions and "get to know it". Even small expenses can add up in this pursuit, ask anyone who has attained the near martial arts oneness with lifeboat matches ;o)