A stainless steel clamp holder and screw fastening secure this feeder/drinker cup firmly in place. It contains metal-style coop cups that stand up well to beaks and claws. Claws and pecking beaks have a hard time breaking down these metal-style coop cups. For cages with more raucous birds, this kind of coop cup is the best option. The Chicken Coop Cup with Clamp Holder, in addition, is perfect for mounting straight to a wire cage. There are 5 sizes available. 150ml, 300ml, 600ml, 850ml, and 1.35ltr.