Small, light weight and most importantly last 2 + hours powering my goggles. This is the best solution I have yet to find for goggle power lasting over 2 hours. It is also very, very affordable and I keep several around as two of these will last and last and last.
These are nice replacements for the stock Fatshark batteries. And you can charge them using 2.6 amps which cuts charging time down drastically. Highly recommend.