These are single-lined, thin, high stretch neoprene boots.

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.In this case, warmth is considerably increased and it is also easier to put on your wetsuit.