4 sizes, made with a double sides, recycled fleece, and double sided velcro so they stay on.  Mulvey likes to go swimming in show banks and when he comes out still wearing all the booties, I have done my job.  All 4 sizes are reinforced at the toe and pad with Slip-Not, a rubberized fabric that is soft enough for Fido to grip through but keeps his toenails from poking through.  It is said to be flexible to 40 below zero.  I've tested it at 20 below but I don't go out if it's any colder than that.  If you do, let me know how it works out.
  Small-paw width up to 2 inches
  Medium-paw width up to 3 inches
  Large-paw width up to 4 1/4 inches
  XL-paws like a Sasquatch