It's perfect for a 500ml bottle, or a bigger bottle on a road bike. Primarily a road cage stick it on the seat tube & the finned rubber retainer and "top bit" of carbon ensures a sweet hold on the bottle over smaller bumps.
It is designed for the average sized bottle (230-235mm circumference is a good fit). Some larger bottles of 240mm+ will not fit. The MT ZOOM big mouth race bottles fit nicely.
Less than 10g of material and you are really pushing it - there are a few lighter cages in the world, but you typically will have to buy a special conical shaped bottle (which then gets stuck in the cage) and pay a whole lot more.
More info here: www.mtzoom.com