the double layer sandal definitely have more support than the single layer . better choice and definitely worth the extra few buck . the `` break in '' time be about a week . it be not too bad the `` break in '' time as some of the other reviewer have say but after it mold to you foot , they be very comfortable and will only get better with time and usage . the strap be tight in the beginning . the size do run a bit small . I wear a size 9 man medium and order a medium -lrb- 8.5 - 9.5 -rrb- and it fit the length of my foot barely , but if I order the next size up , in the long run , it will look a bit too big . like other say , if in doubt , order the next size up . the sandal be narrow and will be tight the first few time you wear they but will be worth it . Mine be so comfortable and I have be wear they every time I step out the door . I walk my dog in they , run errand in time , go everywhere with they . I buy color gray and sierra brown . if you like the sierra brown color , I would suggest order the dark brown color because with wear and tear and footprint , the dark brown will not be as noticeable when it get dirty as the sierra brown .