I really like this hat.  The quality is very nice.  The flex-fit feature is very nice as well.  For me, I wish they had a size in between the two size offered.  In the end, I will order more of the small/med.  My head measures 22 1/2.  The large fits but seems slightly loose.  The small/med is snug, but not too tight.  If my head were 1/4 inch bigger I would prefer the large.  I bought 2 of each size and each hat matches exactly the other of the same size, even though I bought several different models.  I plan on ordering more.