Amazon customer service was excellent when I needed to return these shoes because they were to large.  Apparently the sizing system for Crocs different. I ordered US 8M but what I received was W8 . At first I thought I was reading the size upside down but that was not the case so I called CS to get instructions to return these for the correct size. I promptly received another pair but they were identical(W8)  I promptly received an explanation from Amazon.that the W stood for "womens" I guess a lot of men order type of shoe and the M stood for men's
I like the Crocs brand and have other pairs but would not order these on line again.  They need to be tried on before purchase .