Typical Size of Campfire Lighter Flints -Cerium Sparking Flints:
3/8" Diameter x 4" Length ( 3/8" x 4" ) or 9.525mm Diameter x 101.6mm Length
Reference weight : 1.61 oz/rod or 45.92 gram/rod approximately
Reference quantity per pound : 10 rods/lb or 21 rods/kg approximately

Some find that the hard part to using a ferro rod is not generating the sparks, but getting them to land on the tinder and not go all over the place (watch out when using a ferro rod around synthetic materials such as waterproof jackets, tents of basha sheets - the sparks can easily burn holes through these materials).  The best way to get the sparks to land in the right place and minimize the sparks that land in the wrong place, have plenty of tinder and make a nest for the ferro rod.  Place the tip of the rod in the middle of the tinder and scrape the metal edge down firmly along the rod. If you have less tinder, do the same and make a smaller nest of the tinder and place the tip of the rod in the middle of it.  However, this time, instead of moving the scraper down the rod, pull the rod up against the scraper.  This is harder to pull off successfully but when you perfect the technique it does tend to focus the sparks better. 

Corrosion can be a bit of a problem with ferro rods - especially in hot, humid climates or where the ferro rod is kept close to the skin.  A quick and easy solution to this is to paint the rod with nail polish - clear if you want it to look neutral or a more "exciting" color (such as red color) if you want to make it easier to find if you drop it outdoors!  The surface coating doesn't affect the performance of the ferro rod as far as the amount of sparks it generates but you do have to keep on applying the nail polish though. Suggest getting two rods, one to play with and one to keep in the survival kit, one is bigger diameter and another is smaller diameter to save your money.

As well as keeping an eye on your rods for corrosion, take care not to drop them onto hard ground as they can break (although they can still be used).

You do need to remember to practice with your ferro rod before you need to rely on it!

You can get a bare rod or ferrocerium blanks and roll some tape on as a handle, that will give you twice as much ferro to work with and may save a little room as well. You simply pull your knife blade or striker slowly and firmly down the length of the ferrocerium rod, and sparks easily ignite a stove, barbecue, paper, dry grass bark, tinder, this iron rod is water resistant, and its 3000° C spark works well even when conditions are wet, cold, and less than optimal. this ferro cerium flint fire starter is a favorite of survival experts, hunters, fishermen, backpackers, campers and boy scouts, etc.,  Also the ferrocerium rod can be inserted into one side of Magnesium block to build a Magnesium Ferrocerium Firestarter, etc.,

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