The camp chair I bring on my river trips doesn't have a cup holder, so I started using these mesh cup holders from Down River Equipment. They are made of heavy duty mesh with velcro straps, so you can strap them anywhere (chair arm, raft frame, etc). When I started hammock hanging on the river this summer I found that they worked great on my ridgeline. I have two, and I can slide them up and down the line where I want them. One holds a water bottle, the other holds my headlamp/I-pod/etc. I love having multi-purpose gear.