That thing is a piece of junk.
There are only TWO magnesium block firestarters that are solid, reliable and actually work. The first is the original Doan magnesium firestarter (They invented the thing for the US Airforce). The second is the ones sold by firesteel.com.
*ALL* others that I have tested are a crap shoot. Some work, some don't. All are much more difficult to use. They are very hard, and difficult to scrape.
What happens, is they all (except the two listed above) source the cheapest manufacturer at the moment, and slap thier name on it. So you may buy a "Coleman" for instance. It may work. But the very next one you buy won't. You can simply never tell which ones work, or don't. Same with harbor freight, farm and fleet, or any other generic ones on the market.
There is a huge variance in the quality and purity of the magnesium too. You may buy one, with a higher level of magnesium, and it will work better. The very next one, from the SAME brand, on the SAME shelf, bought at the SAME time, will be so low in magnesium content that it won't work if you put a torch to it. There is no way to tell.
In my experience, ONLY the ones who invented it (Doan manufacturing), and the ones from firesteel.com are held to exacting standards and magnesium purity. They are the only ones that work every single time. They are the *ONLY* ones you can bet your life on.
Now, that said, the magnesium block is really the old fashioned way of doing it. It has big draw backs. For one, the strikers are super small, and get used up quick. Also, the magnesium is in a small, difficult to handle block. We have much, much better options today.
Today, you can buys a firesteel of any size imaginable, from really small, to mammoth 1"X6" sizes that will last a lifetime. This is a significant improvement on the tiny striker found on the old fashioned magnesium block.
Additionally, we can buy almost pure magnesium rod, of almost any size, to go with your ferro rod. The significant benefit is that you can get a nice 5" magnesium rod that is easy to handle due to it's shape and size, compared to the tiny little block of the old days.
Another very significant benefit of using a magnesium rod, over the block is it's over all shape. A rod is simply easier the extract shavings from because it is round.
Buy a 1/2"X5" firesteel from firesteel.com, and a 1/2X5" magnesium rod from them, with lanyard holes, add a good metal cutting sawzall blade to make your shavings and strike the rod, and you pretty much have the ultimate firestarting system.
With a little skill, you can get fire in almost any conditions, short of a hard downpour.
Magnesium burns at 5400 degrees. That is hot enough to separate water into it's base elements of Hydrogen and Oxygen...and then ignite them.
Whatever you do, DON'T trust your life to the junk linked to below.