Part of Sea to Summit's Alpine Line, the Sea to Summit Alpine ApII Sleeping Bag is finally available to the public after years of development and testing. Packed with cutting edge technologies and innovative new features, no expense has been spared in the development and design of these bags. The most technical of these bags, the Alpine Line, were designed for high altitude mountaineering, ski touring, and cold weather expeditions in some of the harshest environments known to man.
When it comes to practical use in the backcountry, consumers expect a compact size and a light carry weight for maximum versatility and that's why Sea to Summit refuses to compromise using only 850+ Lofted European Goose Down. The highest quality down that industry standards allow, Sea to Summit has the down used in each bag individually rated by a third party independent laboratory and packages the report with the bag for specific details regarding quality of the down and its fill power. It is this high-quality down that allows these bags to be so lightweight and compactible without sacrificing thermal efficiency.
The sleeping bag industry within the United States is notoriously unreliable when it comes to temperature standardization, and that's why Sea to Summit has opted to use the EN Temperature Rating System. Drafted by the European Union to regulate Europe's Sleeping Bag industry, the EN system uses heated mannequins in climate-controlled chambers to standardize the temperature rating system across multiple different brands providing three ratings, comfort rating (the temperature at which a 'standard' woman would sleep comfortably for 8 hours), lower limit rating (the temperature at which a 'standard' man would sleep comfortably for 8 hours), and extreme rating for survival situations. Within the Alpine series, the ApII carries rates at 16°F for comfort, 5°F for lower limit, and -31°F for extreme.
Sea to Summit also introduces a groundbreaking new technology within this series of sleeping bags known as 3D NanoShell. As vapor leaves your body it passes through the down layer and, theoretically, evaporates from the face fabric into the surrounding air. In reality, this vapor will often condense on the inside of the shell fabric and moisture is easily trapped within the down, especially if the shell fabric is weatherproof. Over multiple days of packing and unpacking, wet down mixes with dry down decreasing loft and overall warmth. Sea to Summit's 3D Nanoshell utilizes a synthetic layer under the shell fabric of the bag that stops water vapor from moving back into the down. The NanoShell Face on the outside of the bag is amazingly breathable and allows vapor to pass through it easily, further speeding the evaporation process.
Beyond technical innovation, Sea to Summit has utilized a common sense approach to their sleeping bags which maximize efficiency while cutting unnecessary weight and cost. The contoured mummy-fit in the Alpine ApII keeps warmth close to the body while an oversized neck collar, hood seal, and zipper draft tube keep heat from escaping. The security pocket within the bag is easily accessible and catch-proof zippers ensure a smooth operation without the chance of catching the excess down around the draft tubes. The side block baffle construction reduces down shift in the chambers above your torso and legs when you're moving around. A reverse differential cut on the bottom of the bag allows down to loft up around your body ensuring warmth from both above and below. Every brand of sleeping bag on the market has its individual technologies and innovations that provide different features to the consumer, but Sea to Summit has used a different approach with their bags: to create a bag that spares no expense to solve every problem that hinders sleeping bag performance. And as a result, their new sleeping bag line, and in particular the Alpine Series has already made a name for itself as some of the highest quality bags that money can buy.