Drysuits - Neoprene show info...

Neoprene is a type of synthetic rubber, often also used in neck and ankle seals in drysuits. Neoprene can be specially prepared to contain millions of tiny enclosed air bubbles, forming a buoyant and thermally-insulating material. This is called "foamed neoprene" or "foam-neoprene" (not all neoprene contains foam).

As foam-neoprene tends to shrink over the years as it out-gases and slowly becomes more rigid. An alternative is crushed or rolled neoprene, which is used in the construction of all Northern Diver neoprene dry suits and is less susceptible to volume changes when under pressure, and shrinks less.

Crushed neoprene dry suits provide some insulation by themselves (unlike membrane dry suits), but even with foam dry suits, thermal under-suits are usually worn. With a crushed neoprene suit, less insulation is needed underneath.

The undersuits usually vary from a fine base layer similar to the Northern Diver Thermalskin, up to a thicker layer like the Northern Diver Arctic Base or Metalux Arctic. Some people also use a standard wet suit (worn dry), or polyester fabrics used in mountaineering and other cold weather uses (these may also be in pieces, including vests or sleeveless vests). Such fabrics also ultimately insulate in the same way as foam, using air in which convection is retarded by the small sizes of the air spaces. However, per volume and weight of fabric, the best-insulating dry polyester fabrics are more effective than foam, because their air pockets are smaller.