Slimduct® professional construction offers strength and longevity all can appreciate. Offered in 3 sizes, they carry single/ multiple exposed linesets, and come in 3 color choices. Complete line of fittings assures each system is finished professionally. Slimduct® Reducer, 5-1/2 in W to 3-3/4 in H, For Use with: Slimduct® Lineset Ducting System, PVC, Brown, Import