The Tinder Tube is an excellent firestarter. The cord is 100% cotton which is great at catching a spark. Initially, you have to light it with a match the first time - then you pull the smouldering edge/end into the tube, which does two things. It snuffs out the smouldering edge and preserves the charred edge for the next use.
When you are ready to use it to light your fire, push out an inch or so of cord, place charred edge on your flint, strike with a steel and the charred edge of the cord springs to life. Many have found this to take a spark far easier than charcloth.
You can then put the smouldering end of the cord into a tinder nest and breath life into it to light a fire.
When you are done, pull the smouldering end back into the copper or brass tube and the smoulder is snuffed out almost instantly. The delicate charred edge is then protected from damage, ready for the next use.