I bought a size small
I bought a size small and it fits perfectly/slightly loose. I use an action cam on the chin bar yet the helmet does not flop around much at all. For reference, I have a 56. 5 cm head and fit a Specialized Camber M perfectly. The adjustment for the strap does come loose quite often so just give it a tug when you put it on. Note it did not come with different size cheek pads in the box. The color is slightly pale, but in the sun it's still quite vibrant.
Gary S.