I've got an old 70s "bike boom" bike that doesn't have braze-ons for a bottle cage, and finally decided I needed a solution. This QuickCage was exactly what I needed. It's easy to install, and quite sturdy. The velcro strap used to attach the cage to the frame is really long, so if you have an irregular-shaped or large downtube or seat tube, this probably has a good chance of fitting. Then you can just trim off any extra strap once it's mounted.