One shell does three jobs here: it weighs down a patio umbrella, holds a 21-in tray as a garden end table, and becomes a planter box once that tray lifts away. The bag inside fills with 175 lb of sand or 14.5 gal of water, so the empty 21-lb base is easy to carry out and heavy once it settles. Two hand-turn knobs clamp the pole and the tray, two adapters step the socket down for 1.5-in and 1.9-in poles, and a pair of wheels with grab handles let the filled base roll across a deck. Molded HDPE panels carry reinforcing grooves, and a bottom drain hole releases rain from the soil.