From the manufacturer:
Circular rotary replacement blade for the popular 45mm rotary cutters used for quilting, sewing, and general crafts. Cuts up to 6 layers of fabric. This blade is made of high quality tungsten steel for unparalleled sharpness and superior edge retention.
For Original 45mm Rotary Cutter (RTY2/G), Deluxe 45mm Rotary Cutter (RTY2/DX) and Quick-Change Rotary Cutter (RTY2NS).
2 blades per package.