Flagstone Pavers Stonegate®11017678T.GC Wall Block Grey / Charcoal Tumbled. Stonegate® combines an elegant weathered stone appearance with almost endless design possibilities. This versatile retaining wall system allows for the easy creation of gravity retaining walls up to 3-feet in height, free-standing walls and outdoor living elements such as kitchens, fireplaces, fire pits, benches and more.