From Velo Orange :
Use these clamps to add a bottle cage mount to an otherwise mount-less downtube, seattube, or any other qualifying tube.
They're available in pairs in 28.6mm and 31.8mm diameters in Silver and Noir finishes.
Bottle cage not included.
Quick tip for installation: for perfect placement, attach the clamps to the bottle cage first, and then install on the bike!
*photo by Velo Orange