Mesh
Mesh or single lined is the term for neoprene without the usual external nylon coating. It is very flexible and thus more comfortable than nylon coated neoprene and also warmer in strong winds.
Mesh should only be used in carefully chosen areas of the suit as it is more prone to damage from sharp objects.  Flatlock Stitching
Flatlocked is probably the strongest and most comfortable type of summer 3mm suit stitching technique.