I wear a size 10 wide tennis shoe, i ordered the large size boot, says  fits 9.5 to 11 shoe , they are very hard for me to get on, and they are very tight, I bought these last year and they are still in great shape, and light weight, but I should have ordered the XL, would have made it much easier to get on and off, If you are going to wear these boots over tennis shoes,  get the next size bigger FOR SURE and if you have a wide foot, you may want to jump up two sizes"" UPDATE I WEAR SIZE 10 WIDE 4E NEW BALANCE TENNIS SHOW, I ORDERED THE XXL AND THEY ARE HARD TO GET ON FOR ME HAVE BACK PROBLEMS AND BENDING TO TUG:: ON IS HARD IM GOING TO ORDRE ANOTHER PAIR OF XXXL