Bird Diapers will protect you and your furniture from poop, protect your bird from the effects of mild plucking and act as a bid harness - if you attach a flight line.
All sizes listed per bird type assume that your bird is an adult.  If you have a baby bird - you will need to select a smaller size. if you are not sure what size to pick - ask the Fairy.
Also, you will need to train your bird to use a flightsuit/diaper - if you don't have the time for training - you may find it easier to use a BIRD CAPE or a BIRD HARNESS instead.
If your bird has serious plucking issues - you will need to look at a FEATHER PROTECTOR which is much more robust.