Constructed of rust-resistant steel upright and resin base, this 30lbs 18" round diameter umbrella base could support your umbrella securely and evenly in place for a long lifespan, which is a really practical addition to your backyard or your patio area. Thanks to a coupler design, the umbrella base fits 38mm to 48mm in diameter umbrella poles (by adjusting the adapter). In addition, it comes with a hand-turn knob for securing the umbrella to the base. Thus, this 18" heavy-duty round umbrella base is an ideal choice to place your beloved umbrella to beautify your surrounding environment.