Better half & I have been trying different combinations of headgear to ski comfortably in freezing temps for decades. Decided to try this Combo Clava as a one quiver solution to wear under our helmets. Trolled the 'net looking for how to best pick the correct size. Best advice was from a site that recommended measuring around the head from the middle back of the head to 'just under the nose' in front. In spite of rather differently shaped heads, we both came in at approximately 22". According to the Seirus size chart provided by BackCountry.com, this would put us right in the middle of the S/M size.
Upon arrival we tried them on and found they did fit, BUT after wearing them for a few minutes, with & w/o our helmets on, a definite unpleasant pressure on our noses was noticed. And then we pulled the head-covering back to wear it as a 'face mask only' and it was obviously too tight. Checked the size chart yet again to find that 22" is within the very lower range for the L/XL. So they are going back for an exchange for said L/XL. Hope they are not too big around the eye area where the goggles are supposed to fully cover all exposed areas. We shall see...soon! Love the free 2-day ship :-)