These jars are ideal for large milling jobs with their wide neck openings and integrated rubber rings, they allow for easy emptying and do not leak during milling. These are not heavy duty jars, and are intended for running with ceramic media. Charging with steel or lead milling media may overload and cause eventual failure, esecially ith the 10L and larger jars. Made from high density polyethylene. Avaliable in 3lt, 6lt, 10lt, 15lt, 20lt sizes. Please see the appropriate listing for the volume you would like. High Density Polyethylene (HDPE).