Black Diamond, 50 lb., Medium, Blend of Carbon Slag Sandblasting Abrasives in Black and White Bags, Superior Cleaning Capacity, Thanks to Hard Angled Particles that Improve Speed and Cut, Low Free Silica, Low Consistent powder and uniform weight, chemically inert hard angle pieces improve speed and cutting, very low fracturing means less fracturing or chipping Consistent uniform weight and gradation ensure no low clogging heavy metals.