Topp Industries' new polyethylene plastic landscape rocks hide unsightly vents, clean-outs, well pipes and much more around houses, offices, manufacturing plants or wherever needed. The rocks provide a "real rock look" and come in charcoal gray, white granite and sandstone to coordinate with any landscape design. Weather-resistant, the rocks have a standard bottom opening of 9 1/2" ID that can easily be increased to 18" ID at the site. A molded-in weight tray that is filled with sand, concrete, dirt or gravel onsite keeps the rocks from moving. They are available in three designs: Trock36, measuring 28"d x 41"w x 36"h; Trock17, measuring 21"d x 18"w x 17"h; and Trock24, measuring 19"d x 17"w x 24"h.Topp Industries.