These are the small capacity Hardin 1 kilogram high purity graphite crucible. It is used to hold your precious metals such as silver, gold, and copper while they are melted at high temperatures needed in order to cast into bars and ingots. Has a little groove at the top to easily grab with tongs. It's recommended that you never fill the crucible to more than a 2/3 to avoid spillage. Tried and tested on the Hardin 234 electric melting furnace. These crucible can be used multiple times when handled with care. Oil from your hands will speed the corrosion process after heated. Flux also shortens the life span.