Ceiling Hangers shall have a steel frame formed to minimize height by holding an 11/2 x 1/2 ceiling channel on either side of an AASHTO Bridge Bearing Quality LDS Rubber Element molded with an integral lock in grommet at the bottom to prevent steel rod to housing contact. Dynamic Stiffness shall not exceed 1.4 nor the corrected frequency 8 Hz. Ceiling Hangers shall be Mason Industries CRCH. Submittals shall confirm AASHTO Quality and Dynamic Stiffness in addition to frequency.