The Dark Energy Poseidon Nano 3000 mAh Power Bank snaps directly onto MagSafe-compatible devices and charges wirelessly at 5W, so there is no cable to dig out when a battery warning hits mid-hike. The leather finger strap and logo power button with auto shutoff work together to keep the bank ready to use without draining itself between trips. What Our Gearhead(R) Experts Are Saying:"I clip this to the back of my phone before a long day out and forget it's there. It's thin and light enough that it disappears in a pocket."