Diamond Disc 300mm For Porcelain 179SET300BS Segmented. This blade is made with a new technology it is called “Sandwich Technology” these blades are made up by three layers. All three have the same characteristics in terms of diamond but the binder metal changes. The 2 external layers have harder binder metal than the central one. This allows the blade to wear uniformly avoiding the typical round edges in the external part of the diamond rim (than would compromise the effectiveness of the blade). So this feature results in better smoother cuts and longer life of the blade. Highly recommended