Ceiling Hangers shall be fail safe and include a steel frame containing 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. Housing configurations shall be offered to accommodate bolting to structure and simple attachment to 11/2 x 1/2 channel, 12 gauge wire top and bottom or 12 gauge wire on top and 11/2 x 1/2 channel on the bottom. Ceiling hangers shall be Mason Industries type HDCC, WHD or WHDCC as required. Submittals shall confirm AASHTO Quality and Dynamic Stiffness in addition to frequency.