The uppers are made of a low density neoprene with Nylon II inside and out for superior comfort and stretch. The sole of the sock is made of a super low density/stretch neoprene with Nylon inside and super hard-wearing and puncture resistant BSD material on the bottom. This is further backed up with PU dots for added durability and grip.
The top of the toe is made of Powertex and the heel, while still made of soft Nylon to prevent chaffing, also has PU beads for protection against rubbing on the inside of your fin.
p.s If they feel funny when you put them on you've probably got them on the wrong foot.