Lumbar, waist packs.
A very functional derivative of the once popular "Fanny Pack," lumbar/waist packs offer an alternative to the conventional backpack design. Many designs offer some with hydration systems, or conventional two/three compartment design. The most popular has two external water bottle pockets on either side for easy access to liquids while on the trail/route without having to take the pack off. Another feature some packs have is the "Strappettes," which offer straps to be slung over the shoulders to help balance the weight on some larger packs. Some packs are made from recycled plastic bottle material to help reduce pollution and protect the environment.
Some people prefer these packs to the conventional backpack due to a more balanced weight distribution along the waist, and also allowing the back be free from sweat accumulation during more strenuous activities. These packs range from very small to large to accommodate different items depending on the use.