Patented AutoValve™ design speeds reprocessing of sprues and buttons. Use with the patented AutoValve disc insert. This economical C-20 graphite crucible is created from an extruded graphite material that's well suited to working with silver, lower-karat yellow gold (14-karat or less), brass, bronze and other copper-based alloys. For white gold or higher-karat yellow gold, choose a crucible made from denser C-50 graphite. Graphite crucibles help scavenge any remaining oxygen from your melt, reducing oxidation of the metal and delivering cleaner casting grain and alloy. Design features five 1.8mm holes.