6.5 gallon carboys can range from 21"- 26" usually...without the airlock. The dimensions on some of the sites selling them say 24" but I just got one that says 6.5 on the bottom and is only measuring at 21". Weird that I know that but I just measured everything out for a 4-tier system since I want to use gravity for everything until I need to siphon to my secondary.