These are very slim, extremely light weight batteries based on Polymer Lithium Ion chemistry. Each cell outputs a nominal 3.7V at 400mAh. Comes terminated with a standard 2-pin JST connector - 2mm spacing between pins, that plugs directly into the battery connector on Altus Metrum flight computers.

Can be recharged with Altus Metrum Adjustable LiPo charger (not included)

Size: 5.5x25x35mm, weigh 9.5g

This battery is very close to the size of a TeleGPS board, would provide about 12 hours of run-time, and thus may be the ideal battery for use with that product.
Note that while this battery is sold as 400mAh cells, the manufacturer varies their process from time to time, and batteries may be stamped with a slightly different capacity.

WARNING:  Unlike most LiPo batteries made for hobby use, these batteries are made specifically for use with Altus Metrum flight computers, and do not contain an over-current protection circuit board!