A sleeve assembly (2) for supporting flexible duct (4) includes a frame (6) with first and second frame sections (10a, b). The frame sections are secured together by fastener subassemblies (8). The sleeve assembly accommodates flexible duct in various angular and straight configurations. The frame can comprise various suitable materials and skeletal or solid-exterior construction. The sleeve assembly is adapted for various installations in air distribution systems of heating, ventilating and air conditioning systems.