Fits like a rubber rain boot,  Very large opening, this may be handy and great for those with thick calves albeit not for me. return policy could be better as they were sent USPS Prime, so they arrived quickly which is good because we have prairie rattlers everywhere.  However return is done by UPS ground paid by me. I purchased a 7 and a 6 1/2 both pairs were large and loose.  I have returned both pair, they are not comfortable.