After reading the reviews regarding sizing problems, I decided to call Tingley directly before ordering the overshoes.  I was told by the Tingley rep that I would need a size Large overshoe to fit my size 11 1/2 sneaker.  However, the Large was too small, so I had to send the overshoe back and order a size Extra Large.  For some reason, the Extra Large was sold by a different vendor than the one that sold the Large.  The vendor for the Extra Large did not qualify for Prime shipping, so I now have to wait about 10 days to receive the replacement overshoe.