Pre-fabricated isolation rail to be manufactured of prime galvanized steel, meeting ASTM A653/653M, with welded corners. Isolation rail shall be designed to connect unit openings to exisitng curb openings via the use of pre-installed flexible EPDM duct transitions. Unit shall have adjustable spring isolators with non-conductive material minimizing sound transitions and designed to provide a minimum of 90% isolation efficiency with 1” deflection springs. A removable EPDM weathershield shall allow access to the isolators. Product shall be a Vibro-Mate™, as manufactured by Thybar Corporation.