The Canon 90-300mm f/4.5-5.6 EF-S is a budget telephoto zoom designed for APS-C Canon bodies only — it cannot be used on full frame cameras like the 5D. It covers an equivalent 144-480mm range on APS-C, making it useful for distant subjects. While modest in optical quality compared to Canon's L series telephoto lenses, it provides useful reach at an affordable price point.

I have used this with my first ever DSLR - Canon EOS 350D (Rebel XT). Quite decent, especially for the price.