Starrett bi metal unique jig saw blades assortment pack. Bi-metal unique - breakthrough technology provides stronger, longer lasting, faster cutting blades. This new technology joins two strips of high-speed steel wires to a backing steel in a solid phase, using the principle of solid-state diffusion bonding agent - totally different from traditional weld or laser bonding processes that rely on metal diffusion as the union agent at the interface. The proprietary (patent pending) solid-state diffusion process generates 170 percent more weld contact area compared to the existing bi-metal high-speed steels. The result is significantly reduced fracture and breakage at the HSS/backing material interface. Soon after initial use, the teeth develop a groove in the very thin center of backing material at the cutting edge. Multi-Edge Performance, as a result, the cutting stroke produces dual chips that are more easily removed from the cut. For applications utilizing coolant, more of it flows to the cutting surface. This is the Split-Chip Advantage. Lower cost per cut. Fit both Universal shank and Bosch shank jig saws. They are made with Starrett exclusive bi-metal unique saw technology to resist breakage, cut faster and last longer.