PBB eXtreme Base Layer SystemOThrees Point Below Base eXtreme layering system is STAGE TWO in our multifunctional, interchangeable heating system. PBB eXtreme base layer is extra warm with a double layer of PolarPro Technical Thermal Fleece. This PBB eXtreme base layer set comprises of: Top, Salopette, Socks Male or Female Drysuit and Base Layer are Inextricably Linked Internal thermal insulation for dry suits, we feel, is one of the most misunderstood elements of dry suit