Synthetic River Rock - Grey - Over 125 Rocks For Plant Topdressing, Landscaping, Decoration, Crafts & More High quality artificial river rock. 16 unique shapes. Made from recycled material in the U.S.A. One 5.5 lb bag can cover 3 sq. ft. of space. Over 125 rocks. Lightweight and easy to work with for any project. Great accent for your indoor plants. Perfect as a vase filler and for any craft project.