Bluefire® Type 27 Depressed Center Wheel, 6 in x 1 8 x 5 8 11, 24 Grit, Zirconia Alumina ORS NASCO self locking mechanism High impact ABS case with self locking mechanism High impact ABS case with durable rubber shell withstands heavy use Engineered for abrasion resistance with polymer coated blade Measure accurately using corrosion resistant Tru Zero® end hook Non marring base helps protect work surface Large dimension range provides comfortable fit that is 17% more adjustable than earlier versions Wide cup opening area increased by 16% over earlier versions New unique memory foam combines denser and softer foam than previous models A blend of R&D advanced chemistry and shaped zirconia alumina abrasive and premium aluminum oxide grain Excellent performance to price ratio for lower total grinding costs