When you buy a new brewer or dripper, the maker will usually indicate what type of filters go with it. Otherwise the shape should tip you off to the correct filters to use. What we call the "Flat-V" was developed by Melitta way back when, so it is sometimes called a Melitta filter. That's confusing because Melitta makes other types, like basket filters. The filters that come to the point are sometimes called V60 for the name given to them by Hario. But those are made by others as well.