I wear size 11 and my toe is hanging off the side.  I'll be glad when Amazon forces these companies to give a little more material.  I buy size 11 from Macy's or Nordstrom and it fits.  On Amazon, they fit like a 10 or 10 1/2. Annoying!
Someone suggested getting grips to prevent my foot from sliding down.  If that doesn't work, I'm sending them back.