This porcelain crucible is glazed and can withstand temperatures up to 800 degrees C without cracking, exploding, or deforming. Each unit comes complete with base and cover. 

A crucible is a cup-shaped piece of laboratory equipment used to contain chemical compounds when heating them to very high temperatures. The lids are typically loose-fitting to allow gases to escape during heating of a sample inside. Glazed inside and outside except for outside bottom surface.