At Architectural Depot, we bring you both large and defining accents, as well as small finishing touches that refine your decor. Take your trim to the next level with the addition of a urethane keystone. The flat keystone is designed for use with the 9" and 10" crosshead with bottom trim. The back of the keystone interlocks with the moulding profile for a perfect fit. The flat keystone is molded with precise detail in high quality polyurethane. Rigid and dense urethane is strong, but also lightweight and easy to work with. Urethane trim and keystones convey the elegance of traditional accents while offering the high performance of a modern polymer.