I work at the stables and bought these to wear.  I noticed not long after wearing them that my left heel was starting to get wet.  It progressively got worse and now only after wearing them for two months part time, both feet get completely wet.
Someone else at my stable said the same thing about her muck boots which she got a tractor supply store.
I think if you pay more and buy them directly from Muck Boots, they have a good warranty.  I have to look into that because other than that they are very comfortable but it MUST be waterproof!!!