The one-piece inner suit for the climb up to 7000 metres where overheating is a common problem. The two-piece outer a quick overfit to bring the combined double suit up to full summit performance at 8000+ metres:
Incredibly, the Expedition Double Suit is lighter than traditional one-piece down suits as well as being more comfortable and versatile.
"The PHD Expedition Double Suit allows you to utilise the insulation you're carrying lower down, climb through greater temperature ranges & be more comfortable & adaptable. The materials used are on the cutting edge of design for high altitude gear and the build quality is exceptional."
Innovative features include: —Heat-pad pockets at the wrists —A harness tie-in slot —Lanyard clip loops —Flared storm baffle —Pit zips for maximum venting —White fabric used on inner suit to reduce solar gain
Inner and outer work perfectly together. Inner suit is white to reduce solar gain (heat-exhaustion and fatigue from dehydration often cause more of a problem than the cold in high altitude mountaineering) and has a temperature rating of -10°C (14°F). When the outer jacket and trousers are worn the system will enable you to cope with temperatures down to -50°C (-58°F):
The PHD Expedition Double Suit. Outer jacket (shown) and trousers are specifically designed to work with the inner down suit. Comes in two versions one for -35°C (-31°F) and one for -50°C (-58°F)
For more information checkout the PHD website