Apidura's Expedition Downtube Pack aims to solve the problem of limited water bottle storage by offering a small bag that can be securely strapped onto your frame. It can fit a full-size bottle of up to 710ml with a little room to spare and, even if it is mounted on the underside of the downtube, you don't need to worry about dirt getting on your bottle as the pack is waterproof and features a roll-top closure to keep trail debris out.
The bottle holding bag comes with a strap designed for tubes of 30-60mm diameter and uses grip pads to stop it from slipping or moving while you are riding. The bag itself is made from a lightweight 3-layer waterproof laminate Trilon fabric. With frames featuring less or no bottle mounts it could definitely be helpful for those who like to take a bottle with them to not have to limit their bike choice to only bikes with bottle cage mounts.
The Expedition Downtube Pack sells for $67 // £52 / €59 and is now available from Apidura. You can find out more here