Grey sand stone window sills / lender are an excellent choice for a window sill material. This stone offers a timeless aesthetic that will not only look beautiful for years, but also add a classic touch to any home. Grey sand stone window sills are extremely durable and are able to withstand extreme temperatures and weather conditions. The stone is also resistant to chipping and cracking, making it a great choice for exterior window sills. This stone is also low maintenance and requires only a simple cleaning with warm water and a mild soap to keep it looking its best.