I ordered the Bottle Holster. Actually three. I really didn't have a plan for them but they were not expensive and they were big enough to hold a 40 oz bottle or a 1.5 liter bottle or a tool roll. Fuel? Water? Both?. I don't like water bags on my back so one ended up strapped to my T7 crash bars with a drinking tube connected to my tank bag. Lots or water, no weight. The other one I think will go on the other side crash bar for carry a spare water bottle. I think the last one might be a fuel bottle on the rear rack bag or a place to hold spare tubes (T7 tube tires) or maybe a tool roll holder. These are well built, attach anywhere, are inexpensive enough to buy many and are really well made. Do yourself a favor, buy several and get creative. You will find uses that you didn't even think about. I might need more!