The PRN20392 is a professional grade grinding wheel that is designed for use with the Proxxon Longneck Angle Grinder (LP 150/E). It is 4.5 inches in diameter and has a thickness of 0.25 inches. It is made of silicon carbide, making it the ideal choice for harder materials like masonry and steel. This grinding wheel is also an excellent choice for sharpening edges on blades and tools.