4 Sizes to choose from: OFS7A - 20" high, 8" x 9" at base OFS7B - 30" high, 6" x 7" at base OFS7C - 40" high, 10" x 11" at base OSF7D - 60" high, 9" x 11" at base All sizes use 3/4" Inlet Tubing, and 200 GPH Recommended Flow Colums and boulders have long been a favorite choice when building bubbling water features. Each of these pieces have been molded from actual rocks for a very realistic appearance. Each rock may vary slightly in appearance and size. A great way to make an interesting display. The columns can be used in many different combinations, each one being unique and beautiful. Because columns are typically used in multiples, recommending a pump or basin is difficult. Generally a 48" or larger basin is used when three or four statuary pieces are installed together.