Flashlights, cameras, and other electronics eat up batteries, meaning spares are always a good idea. Batteries do not play nice with water, so why not protect them in a durable, waterproof, and convenient capsule?
The Talos capsule is sized to fit lithium batteries, particularly CR123 or 16340/RCR123 sizes. The capsule interior is made slightly oversized to accommodate larger batteries that are not exactly 16mm x 34mm. To avoid rattling issues, foam pads are on the top and bottom of the capsule to hold the batteries in place and prevent the batteries from making contact with the aluminum of the capsule. The entire capsule is also anodized with type III hard anodizing to both prevent scratches and damage as well as add a layer of redundancy with making contact.
Since many lights take more than one battery, an optional extender piece can be added on to allow for the addition of another battery. Have four batteries? Add three extenders. The width of the capsule is perfect for an 18650 or other battery with an 18mm diameter.