I usually buy the Olfa replacement blades for my rotary cutter. Even with a 50% coupon at Michael's, they are about $7 each. I have picked up a package of 6 45mm blades made by Singer off the clearance at Walmart. The package was $10, so a little less than $2 a blade. I wasn't sure if they would fit but they do and I am pleased to have a good blade supply for a while. Even if they only last half as long as the Olfa blades, they are still a good buy.