Shoulder bag to the weight of the bag spread over two shoulders, and will therefore reduce the negative weight of a single shoulder. Second, shoulder bags the most important position in the human spine, the middle of the body, so will not cause excessive loading capacity of a side.

Dual shoulder bag the bags in the weight-sharing on the two shoulders, and it will be a single shoulder reduction of negative weight. 2 double shoulder bag, the weight of the spine in the human body, that is the human body in the middle, so it does not cause a particular side of the gravity.

The shoulders package shared the pocket weight on two shoulders, therefore could reduce the single shoulder to carry a heavy load the quantity.Two comes, shoulders package of heaviest position in human body spinal column place, namely human body among, therefore cannot create some one side the beari

Double shoulder bag bags spread the weight of the two shoulders, and will therefore reduce the load of a single shoulder. Secondly, double shoulder bag at the most important location in the spine of the human body, that is, right in the middle of the body, so it does not cause a side loading capacit

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