Roundup Dual Action Weed & Grass Killer Plus 4 Month PreventerThe dual action formula of Roundup kills existing weeds and prevents new ones from growing for up to four months and it kills them down to the root, guaranteed! Plus, the Weed & Grass Killer can be used on driveways, sidewalks, patios, along fences, curbs, retaining walls, and edges of lawns, as well as on decorative rock or gravel areas. Simply add 6 fl. oz. of the concentrate to 1 gallon of water. Rainproof in 30 minutes and visible results in 6