Buying the right part, explained

The specifics behind the match — finding your model number, when to change, and what "compatible" really costs you (and doesn't).

The model number is the whole game for buying the right filter. Where each brand hides it, and what not to confuse it with.

The '6 months' on the box is an average. What actually drives it — and how to tell your filter is spent without guessing.

The honest answer: the filter media is rarely the risk — the fit is. What to check, and the one category we won't sell.