Semi-autogenous Grinder (SAG) utilizes grinding balls like a ball mill. A SAG mill is usually a primary or first stage in the grinding process. SAG mills are characterized by their large diameter and short length as compared to ball mills. SAG mills are primarily used at gold, copper and platinum mines with applications also in the lead, zinc, silver, alumina and nickel industries. SAG uses lifting plates along the interior of the drum, which lift material throughout the rotations, causing them to fall onto one another to promote crushing.