Устройство идентично CI 109, но CI 121 имеет меньший диаметр и легче на 0.5 фунта.

Features a tapered glass laminate housing and die-cast aluminum base. Offers standard mounting and appearance to many Cessna communication antennas. The CI 121 has been re-tested and upgraded to the new RTCA DO-160D environmental requirements and offers the 118 to 137 MHz frequency associated with DO-186A MOPS.
P/N: CI-121