From the Manufacturer:
Straight Blade: Perfect for crisp, controlled cuts on a wide variety of materials, these blades fit most 45 mm and 60mm rotary cutters on the market today.
Perforating Blade: Prepare fleece blankets for crocheting or stitching, perforate forms, make raffle tickets and more with this unique Perforating Rotary Blade, which fits most standard 45 mm rotary cutters.