26" but that is the minimum length. If you are packing if in a hard side bag, you will want a good 26.5 inches of space.
I bought two of these & I never use them because they really don't allow that much tilt. An ideal condition would be to have an adjustable joint below the zippered opening, rather than inside. But if you are happy with sending your light almost straight on, they will be great. They are sturdy and we'll made.