Market standard base: This patio umbrella base stand is equipped with rubber adapters that fit the market standard umbrella pole diameter: 3.8cm/1.5’’, 4.8cm/1.9’’. It can fit into most patio umbrellas with more choices. Stable and firm: There is a rotary knob on the side of the centre pole to fix the patio umbrella on the base stand, making sure the whole structure is firm and stable. Non-skid design: Anti-skid design at the bottom of this umbrella base makes sure the base stand does not slide on different ground situations. Outdoor umbrella essential: Suitable for umbrellas when used through an outside garden table or freestanding in a wind-free position. Provides a solid base for compatible umbrellas.