Nothing at all wrong with the magnesium blocks. I have used several and they are, IMHO, a step up from most spark rods because they incorporate spark and tinder in one compact package. I had one corrode to nothingness when left in warm-moist conditions, welcome to Florida, and in contact with less noble metal. Rookie mistake.

I still have the second I bought and it is almost new. I lit a fire with it just to confirm I remember how.

I think these units get little notice because, despite the fact they work well, they are simple, cheap and, profit margins are low on them. Sales would go up if a hero in a major movie used one.