The 21894 helps support the boom arms used with the CTS towers. It includes a 30"-long aluminum pipe, a 60"-long aluminum pipe, the 21261 Bracket Set, and two CM230 Adjustable Inclination Mounts. Below the boom arm, the 30" pipe is attached to the CTS tower via the 21261 brackets. A CM230 mount is then used to fasten one end of the 60" pipe to the 30" pipe. The other end of the 60" pipe is fastened to the boom arm using the other CM230 mount.