These are Xbox battery packs for charging. You charge them, take one, and put it in your hand. When it runs out, you return it to charge and take the second one. When the second one finishes, you'll find the first one charged, and you take it to charge. This way, you have infinite charging. Note: They last a very long time in hand. One lasted me 5 days. Price: 40﷼ I bought them for 100﷼ from Jarir.