UnderDuct by Monoxivent provides the most versatile and cost effective Underground Fiberglass Reinforced Plastic Duct (FRP) on the market. We provide a wide range of solutions for the most demanding environments to standard layouts. FRP products are available in straight lengths, standard and custom fittings, or in shop fabricated sections. Single wall duct can be shipped in prefabricated assemblies. Pre-insulated double wall duct has many advantages, including assured uniformity of insulation, permanent protection of insulation, and all-in-one installation.