I have a couple of helmets for mountain biking. They are all Giros (E2 and Xen). They fit my head. I like the Roc Loc 4 feature that these two models have (adjustable cradle). Once you get the chin strap adjusted the first time, you just "zip" these plastic doohickeys open and closed for a perfect fit every time!

Like Irulan, I also go through at least one helmet every season. Helmets are always on sale! When the 2005's come out, all the 2004's are marked down. Sometimes there are changes to the helmets, but usually it's just different color choices each year. I'm willing to wear last year's color to save a few dollars!

But remember, Fit Fit Fit Fit Fit is the most important thing. Everybody's head is a little different.