The 250-125 Metal Concentric Reducer is known for its durability, versatility, and ease of installation with solid plastic ducting, as well as insulated or uninsulated flexible ducting and fan spigots. Featuring male ends on both sides, this reducer is designed to fit securely inside solid plastic and flexible ducting. To achieve a clean fit, fan spigots and duct fittings may require a small piece of duct.