I carefully read reviews of sizing of Keen and Croc shoes purchased on Amazon. Sizing especially with online orders is the most important aspect as this can lead to returns and exchanges that requires time from Amazon and the consumer. For me, the length of the back strap of Crocs Duet Sport is the reason why I have to go one size up . . . this issue is also present with Crocs Crocband. As for comfort, this is the MOST cushy of Crocs and I have several (Original, Beach, Specialist, Crocband, Mercy, Cloud) and was encouraged by other reviews of the more durable sole. I am a size 10 in shoes and typically take a size 10 womens/8 mens in Crocs but will have to order 1 size up in the Crocs Duet Sport. I wish it was offerred with only holes on top as this would limit amount of debris that can enter the shoe if walking on a trail.