If you're running one of Exposure's lights, and you need even more battery life, the Exposure Support Cell is precisely what you need. This secondary battery piggybacks off of your existing system. It's available in three sizes, and as you probably guessed, increased size equates to an increased battery life. The batteries are housed in an attractive carbon fiber case with machined aluminum end-caps for added durability. In other words, these Support Cell make your light even more perfect for pushing the limits well after dark. The Exposure Support Cell is available in the sizes 1. 7A, 2. 9A, and 8. 7A. Please note that this product is only compatible with Exposure lights that have a Exposure's Smart Port Technology (SPT).