Dammit, as some have remarked, I have a big head ... XL in fact.
I have sent a query to vendor (in China as usual) asking about compliance with DOT, ECE 22.05 (Europe and UK), or AS 1698 (Australia) motorcycle helmet safety standards. Apparently AS is best because it tests all batches of helmet somehow, while DOT is just a random testing and ECE is tested for two knocks but not so hard as the AS! Will post what they say.
Thanks Vince.