Question #6 of the official Q&A Forum answers your question, I cut and pasted it below, as well as the link.
http://ftcforum.usfirst.org/showthre...-Playing-Field
The heights of the angle brackets supporting the bottom baton in the Dispenser are listed below. See the attached illustration.
High Dispenser - 9 1/8"
Middle Dispenser - 6 3/8"
Low Dispenser - 3 5/8"
When designing your robot, keep in mind that field tolerances may vary by as much as +/- 1.0" as specified in rule <G12>..