We both have one in the photo with her holding the bass you can see 2 of the 4 bases I put in so I can adjust for sun position. One on each side of her and my seat. I have PVC pipe with clamps screwed into the aluminum seat. Works ok but the umbrella turns with the wind, thumb screw help but they still turn. My 2 are 6.5 x 5.5 so wind will turn them especially when they're tilted. If round it wouldn't make a different. I got them at Walmart $28 each.