This is an adapter to fit various size parasol tubes to various size parasol bases. Perfect if you buy a new parasol but want to reuse your old base, or if you lost your adapter. Most bases has some form of retaining mechanism, so there is a slot for that. If not needed, set the slot width to zero.
Designed for printing with 100% infill. No support should be needed. ABS is a suitable material, but you may want to compensate for thermal crimping (can be done in customizer). PLA has some issues with temperature stability and UV-sensitivity, but at least in temperate climates it may still hold for a couple of years.