A mounting curb is recommended for installing your roof exhauster. This 12" high mounting curb is welded, prefabricated, heavy-gauge galvanized steel with a 1.5" wood nailer and includes insulation, damper shelf and mitered 3" cant. The outside dimension of the square curb is 18 1/2".
The 711218 is for use with SDB, STXD and STXB Size 12-14 and ARE/ARS Size 10 roof exhausters including single and triple phase models.