Surface Area

The heat stored inside the shrab is lost from the surface exposed to cold air, and the amount of heat loss is proportional to the size of the surface area.We select the "proper surface area" that is not too large to keep your sleeping warm even in low temperatures.

3D construction

The cross section of the body is large on the chest and the back is a small rounded shape.This shape is finished with a "3D structure" that has room to the chest so that warm air hugs the body in a three-dimensional way.

Interior space, high uniformity

The most important element of determining the warmth of the sleeping bag is the interior space (= air).The internal space causes heat conduction when the body is too narrow to cause too much contact with the body, and if too wide the air convection and both can lead to heat loss.Our sleeping bags have an interior space that is not too narrow or too wide, providing both warmth and mobility.

The loft of down that determines the warmth of a shruff, is the weight that goes all the way around the sleeping bag.Finished with a "differential cut" design of the outer dimension to ensure that the height of down from the inside creating an internal space is uniform throughout the shruff.