Kits are very convenient. They come with everything except the bottle. You can use a number of different juice bottles that will fit the stopper. This is great because you can keep a supply of clean bottles. Remove the dirty bottle, and replace with a clean one. Also, if you every break one, then it is very inexpensive to replace. All parts are stainless steel.
This style of bottle should be used only with 'Small' and 'Medium' birds.