No matter how good Apple makes the battery life in their laptops, you’re always going to want a few more hours. And though it’s a little bit janky, ChugPlug’s external Mac battery is the best option you have right now.

Today on eBay, you can get a ChugPlug for any MacBook Air or 13” MacBook Pro for just $40, the best price we’ve ever seen. The ChugPlug attaches directly to your Mac’s power brick, and contains a 4,000mAh battery to give you 3-4 extra hours of battery life, on average. It might be a little bulky to keep attached to your power cord all the time, but it’s a perfect safety net for long days away from any power outlets. [ChugPlug External Battery Pack for MacBook Air 11” and 13” and MacBook Pro 13” Portable Charger, $40]

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