From the manufacturer:
OLFA's Rotary Blade 45mm Refill. These replacement blades are made with high-quality tungsten steel for durability and superior edge retention. They cut up to 8 layers of cotton fabric at once and can be used on fabric, paper, leather and other materials. These blades are for OLFA's 45mm Standard, Deluxe and Quick Change Rotary Cutter (not included). This package contains two blades and a plastic container that you can use later for storage. RB45-2, 1079062. Imported.