With a wide, adjustable grip, a rubber ring to steady the cup and a versatile joint that rotates through 360 degrees.
This gadget is marketed to parents as a cup-holder for baby strollers. However I have successfully used it with my wheelchair, zimmer and Taga Bike (a folding tricycle). It is more suited to take-away cups, beakers and bottles than mugs. But the cutaway sides make it easy to push the cup out from below.
The adjustable grip is strong and unlike other stroller cup holders, it opens wide enough to use with my wheelchair and trike. If knocked very hard indeed, the cup holder will detach without damage from the grip. I have tried a number of different cup holders. Most break when accidentally whacked, and some have cracked on the first outing!
For safety do not attach holder above baby or self, but position outward and to the side instead.