The Cressi Soft Boots are single-lined, thin, high stretch neoprene.
The inner is lined in Metallite so they are easy to put on.
The sole has an effective non-slip lining.
They can be used with both closed foot fins for greater warmth and to protect the skin from scratches and chafing, as well as with firm-soled boots, using open-heel fins.
The sox make it a lot easier to put on your wetsuit and increase warmth.