A ball bat includes an outer shell and an insert positioned in a ball striking area of the outer shell. The insert may include a tube element and one or more spacer elements positioned to form a gap between the tube element and the outer shell along at least a portion of a length of the tube element. In some embodiments, the insert or the gap may extend along only the length of the ball striking area. The outer shell may provide some compliance during a hit to create a trampoline effect, while the insert may provide a backstop to limit radial deflection of the outer shell.