Bumpers

[WizenedEE]

http://frc-manual.usfirst.org/viewItem/57#4.1.6

be backed by ¾ in. (nominal) thick by 5 in. tall plywood.

So 5 inches tall

Bumpers must be located entirely within the Bumper Zone when the Robot is standing normally on a flat floor.

[R01-2]
The Robot must have a Frame Perimeter that is comprised of fixed, non-articulated structural elements of the Robot. The Frame Perimeter of a Robot is defined by the outer-most set of exterior vertices on the Robot that are within the Bumper Zone, which is between 2 and 10 in. from the floor. Minor protrusions no greater than ¼ in. such as bolt heads, fastener ends, and rivets are not considered part of the Frame Perimeter.

So they have to be fully contained in the range 2 to 10 inches off the floor.

Thus, the bottom of the bumpers can be from 2 to 5 inches off the floor and the top can be from 10 to 7 inches off the floor. (subtracion)