Universal safety razor blade refills for your plastic-free bathroom. These are replacement blades for the safety razor we sell, but can be used on any double-edged razor. How long you can use each blade really depending on how often you're shaving, the coarseness of the hair being removed, and the amount of surface area you're addressing with each shave. "Up to a week" and "one to 4 shaves" are claims you'll find around the internet regarding the longevity of blades. We recommend you go ahead and buy additional blades (this comes with 5) and make that judgement for yourself after a month or so of use.