Got two of these for my gravel bike- will be getting another for my enduro bike. Holds a 710ml bottle very firmly. Can probably bend them to suit bottles of different shapes/sizes. Haven't had a bottle move even an inch in one, even over bumpy terrain. Not the lightest but these are cheap and strong with a good hold.

Not the prettiest cage. But the best I've found to hold a bottle under the downtube. I have 2 duel suspension mountain bikes and neither have a cage mount inside the front triangle. This thing will NEVER let go of a bottle on drops, jumps etc becuase of the way it is shaped.