Great quality and value.
I don't consider myself having a large head all other headgear I have is medium. This skull cap is marked S/M but it's definitely small. It's a very tight fit, too tight in fact.
A very well made product fits and covers well under helmet ,warm and kept the rain out also looks good when worn without helmet
L/XL fitted my 59cm head diameter. Not too tight or slack. Covers ears nicely and helmet fits snugly over it. Stops a cold head down to about 5° air temp. Half price bargain at the time of purchase, so v happy.
It does what I expect it to do, keep my head and ears warm.