Never miss this oxygen backpack to make your life easier !!! Our Oxygen Backpack is designed for M-15/D size oxygen cylinders, which size fits perfectly to the D tank oxygen cylinder. The shoulder straps are easy to adjust, and the thick design greatly reduces the pressure caused by the weight of the oxygen tank. There is a middle chest strap is also designed in order to the shoulder strap of the backpack is not easy to slip off. Whether you're shopping, walking, or traveling and so on, this oxygen backpack makes it easy to get going! Multiple Holes & Large Pockets Multiple holes allow you to place the oxygen tube at will without worrying about the tube being kinked or exposed too much.