I love these boots. I wear a true 9.5M and ordered a 10M as recommended and the boot fits perfectly with a normal athletic sock. The heel does not slip big time.  I have a narrow heel and found Croc mid calf boots actually  too big in the heel for me, so I am delighted by  the fit. I live on the beach so my waterproof boots are tested everyday on sand and running salt water.  I have had these now for over two weeks. So far these are holding up perfectly and maintaining their shine and cute polka dots. If there is cause for me to modify my opinion I will amend this review. I highly recommend. Please note that these are cut narrower in the calf than Magic Chief. I can still put my jeans and pants inside these boots and I am 58 and 190 lbs. if you have really larger calfs I recommend Magic Chief.  However, I recently returned a pair of faux fur MC because they began leaking  at the foot bed after a month on both feet. An unlined pair I owned did not have the problem. Hope this review helps!  I also love these boots are made in the USA.