Welcome to the board. It depends on the size of your rotary cutter. There is an assortment of blade sizes. 45mm is the most common size. There are blades that can not be use in some rotary cutters since the manufacturer of the cutter wants you to buy their blades. I have Olfa cutters and buy the blades when they are on sale at JAF. Being disable, I now use my 28mm rotary cutter the most.