DS-5B119M 3/2mm: 

The wetsuit's thickness in millimeters. This indicates that the suit has a 3mm-thick neoprene core for warmth and 2mm-thick neoprene in the arms and legs for better flexibility.
F/N: The material construction. This stands for Finemesh/Nylon, indicating the type of neoprene used.
Finemesh neoprene, or "smooth skin," is used on the chest panel to reduce wind chill.
Nylon/Nylon (N/N) is a standard, durable neoprene fabric used in the other areas of the suit.
Fullsuit: This specifies that the wetsuit covers the entire body, with long arms and legs.