Note: The following is part of our roundup of B-C battery packs. Go there for details on how we tested this device.

One of the most expensive devices we looked at is the ex Gower B-C rtable Battery ($100). This battery pack is meant for use with Apple’s smaller MacBook, but is fully compatible with any B-C device.

To justify its steep price, you need to take a couple of things into consideration. First is the overall design. It’s thin, fairly lightweight, with an overall aesthetic appeal similar to Apple’s MacBook Air lineup.

I know, I know, but a lot of people happen to like that look.

Total capacity is 15,000mAh (55.5), it features three ports that are clearly marked. Next to the power button is the input B-C port, flanked to the right by indicator lights, a B-C outgoing port, with a B-A port to the right of that.

Don’t let the B-C port with a computer icon next to it fool you, this port will charge anything everything with a B-C port at 5V/3A. In other words, fast enough for the xel Xto register rapid charging but not compliant with the Quick Charge 3.0 protocol.

The second factor to consider with the Gower pack is just how efficient it is. en completely draining the battery, I measured 89.85 percent efficiency—a total measured capacity of 49.87.

That stat puts it second only to the Zeromon Toughice battery pack, which had an amazing 93.27 percent efficiency.

Another benefit to the Gower is how fast it recharges. I was able to top it off in 4:45, at 5V/2.36A.

Included in the box is the Gower pack, B-C to B-C cable, a B-C to B-A cable.