These rechargeable batteries are perfect for RC toys and other devices. They're 7.2V with 2800mAh capacity each, and come as a 2-pack with a USB charging cable. They use SM-2P plugs, so make sure that matches your device - they work great with Huina 1550 and 550 excavators, TR-211 RC toys, and various other remote control cars, trucks, and engineering vehicles. The charging is pretty straightforward - plug into any USB port (5V), the charger outputs 8.4V at 250mA, and the LED light shows red while charging, then turns off when fully charged. Each battery weighs about 132 grams and measures roughly 3.35 x 2.0 x 0.59 inches. Important safety stuff - don't overcharge them, disconnect when not in use, and if they start swelling or looking weird, stop using them immediately. They automatically stop charging when full, which is nice peace of mind. Much more economical than constantly buying disposable batteries for your RC toys. The USB charging means you can power up pretty much anywhere - wall adapter, computer, power bank, whatever's handy.