Mammoth crocs are the smartest thing that the company has invented to transition the shoe into the winter months. The fur lining is very comfortable, and feels great with or without socks. Often, I don't like to wear socks in the winter, but the only problem is when I don't wear socks with these my ankles will get very cold when the snow comes.
I love crocs, and own multiple pairs. I enjoy the material, the fact that they are so comfortable and now, the fact that they can be all weather!
The lining is warm, thick, and most importantly - removable. It can be taken out and washed. Usually I am a size small in crocs, and it was advised to go a size up because the lining takes up room in the shoe, I didn't feel this was necessary but if my feet were any larger than this may have been an important factor.
The Mammoth model are not available in every color - of the colors that I prefer I had the choice of light pink, or blue - my usual choice of crocs are turquoise, and dark pink so I went for the light pink, and the light lining.
Crocs are known for their quality material, and the lining makes it easier for the shoes to smell - but, since the lining is removable, I guess they covered their bases.