The insert is suitable for the Doppler Umbrella stand with a pole diameter of 40cm (15,7") or 28cm (11").
https://dopplerschirme.com/de/85897axt-active-granitsockel-trolley-70.html
https://dopplerschirme.com/en/85897axt-active-granitsockel-trolley-70.html
The author marked this model as their own original creation.