Hanging hay feeders. These are a great way to feed hay without a big mess. They hang on the cage(preferably inside). 2 sizes available. Small, for carriers 3in wide X 4in tall X 2in deep and large, for cages 5in wide X 6in tall X 2in deep. 
Simply hang and put an extra bend to the hooks to hold around the cage wire better if you have a mischief playful one. 
Please note that I will be making them with a poly plastic backing, therefore hanging inside the cages will be necessary