Our take

Cup holder mounts are only as steady as the holder they sit in, and the expanding base on these assumes a deep cylindrical well of roughly two and a half to three and a half inches. Shallow or angled holders, common in older cars and a lot of European interiors, let the whole thing rock, and a rotating arm multiplies that play the further out you load it. Good for a phone, a coffee and a sandwich. Put a laptop on the end of the swing arm and you will watch it tilt.

Best for: Deep, straight cup holders carrying light loads