I ordered some firesteel blanks from the folks over at ferrocerium.com last week, and had a nice envelope full of fire starting rods waiting for me in the mail yesterday. I ordered one of each of the rods that they sell, just to see how the different sizes compare. I personally prefer these over one of the LMF ones, since the most expensive one at this site is still cheaper than the LMF Scout. I can also make my own handle or lanyard for these, and don’t have to deal with the garbage striker that comes with an LMF.
I played around with them after taking some pictures, and all of them throw some wicked sparks. I used a 3″ section of a crappy high carbon hacksaw blade for the striker. The squared edges of a hacksaw blade seem to do better than anything else once you sand off the paint that comes on the blade. Once you have some flat edges worn into the firesteel after multiple uses, the amount of sparks that come off just keeps increasing.
You have a scrape the coating that the firesteels come with off with a few scrapes before any sparks start flying. The coating is there to prevent rust, and it is a good idea to replace it with nail polish or something similar if you intend on storing a used rod for any extended period of time.
The 5/16″ x 4″ one is probably the most useful to me. 4″ of a firesteel can generate an impressive stream of sparks, and it is slightly thinner than the largest one, which is on the edge of being too heavy. A firesteel will give you several thousand sparking scrapes, so any of the sizes will suffice. I just prefer the larger size for building a comfortable handle and throwing the most sparks.