This cup holder is designed for water bottles and thermos cups. It has an open bottom so the bottles/cups can fit deeper and more securely. The cup holder is also reversible which allows you to raise or lower your drink by a couple inches.
If you need a cup holder that has a bottom for coffee cups etc. check my other design.
I have also designed supports for attaching to a variety of wheelchairs
Cup holder support for standard tube armrest
Cup holder support for Permobil
Cup holder support for under cushion