Greases are available in an array of colors, textures, and chemistries and are primarily used to lubricate rolling element bearings and journals. Despite this apparent diversity, they are all made up of base oil, performance additives, and special thickeners, which hold the base oil in a semi-solid form, which shears to release the lubricating oil. The consistency of the grease is described by its NLGI grade, where a higher number signifies thicker or more solid grease – this is affected by the type and amount of thickener, and to some extent the additives and base oil viscosity.