Hi khaled mohamed,
R is the number of rollers. r is a roller. Raymond mills include 3R, 4R, 5R, 6R. You can select from the fineness of the material that user needs. 5R that is a five roller mill. Liming is a professional milling machine manufacturer,the high pressure suspension mill is the company's patented product which is suitable for crushing limestone, ceramics, slag etc.Mohs hardness is not greater than 9.3, mixed degree below 10% of non-inflammable materials in mines, metallurgy, chemicals and building.