Birds that are not familiar with water bottles should be trained on how to use them. Water bottles are wonderful tools to train your bird on if they tend to dunk all of their food into their water bowl. This variety comes with three different tube sizes. 5/16th is best suited for smaller species and for cages with smaller bar spacing. 7/16th is best suited for small-medium sized species with smaller bar spacing. 5/8th is best suited for medium to larger sized species with a larger bar spacing. 9x3x3