The Schluter KERDI-KERECK INSIDE CORNER 90° is a waterproofing shower membrane designed for use in flooring underlayment. This product, manufactured by Schlüter, comes in a convenient 2-pack and is perfect for creating a watertight seal in inside corners of showers or bathrooms. With its high-quality materials and efficient design, this product ensures a reliable and long-lasting waterproofing solution for your home improvement projects involving flooring and tiles.