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. 7/16th which is best suited for small to medium sized birds with smaller cage bar spacing. 5/8th which is best for medium to large sized birds with large bar spacing. 5/8th Tuff Tip which is best suited for larger birds with strong beaks.