These are lined with suede inside, both the soles and the upper part underneath the tweed. This makes them totally unbreathable and they make my socks really damp with sweat so I end up having cold damp feet - I’ve never had this problem in any other shoes or slippers! I’ve now put woolly inserts from my previous Bedroom Athletics soft soles wool lined tweed pair (which have totally fallen apart after 13 months, which is why I wanted to give these hard soles ones a go) so it makes the problem less severe. Disappointed as I really wasn’t expecting having to take them off regularly to dry my feet or change my socks…