ThermalBuck solves the challenge of installing nail flange windows & doors with exterior insulation by extending the mounting point to create a flush plane for cladding. It also insulates the rough opening, limiting thermal bridging around windows & doors. Made of a high-density EPS coated with a waterproof resin, it's unique "L" shape goes inside the rough opening, and is secured with an air & water barrier sealant* and nails. It's simple to install and easier to flash than a wood buck. Dimensionally stable and strong, it will not warp, rot, or shrink, and helps to support the weight of the window. ThermalBuck outperforms a traditional wood buck, and protects the integrity of your window & door installation. Available in 7 different depths from 1.0" to 4.0" to match the CI and/or rainscreen depth, ThermalBuck is a true continuous insulation solution for the building envelope.