Go somewhere that stocks lots of brands and I bet you'll find that there is a difference in length even for filters matching the PH9837 spec. If you search around on this site you'll also find that different brands can differ a lot in how big the filter element is in the can, though that can be misleading because sometimes the shorter filter element makes up for it with a greater number of pleats and more length. IMHO the advantages of a larger filter are probably marginal, though I use a couple that are oversize. In one case it gives me a better grip on the filter and means the engine can take the full 5Qt. jug at fill up. In another case, the specced filter is so small it makes me feel inadequate.