Well, i tried it with SunConures ,Cockatiels , Senegals and even Budgies and it's amazing ,it's designed in a way that the poop is collected in the pouch designed for it and never touches the skin or even the feathers of the bird , i kept it for as long as 6 hours and never found any trace of poop on th bird's feathers, the main problem's that sometimes the bird's are annoyed with it and starts to chew on it but they soon forget about it and continue what they were doing,but the main drawback is the fact that the bird has to get accustomed to it at a very young age i start introducing it to them even before they are completely feathered ,but getting an older bird accustomed to it is a real challenge cause when they are introduced to it in older age they hate it , that's my own experience and i though i'd share it with you all,i never tried it on a grey ,but i will with my baby and let you know what's the results.