v1 (beta). Round, open-top silicone formwork for hollow vessels: a two-piece registration base, two rigid housing halves with a stepped capture bore and locating pins, and a threaded top yoke + thumbscrew clamp over the seam. Assemble the housing on the base, pour silicone into the open top to make the flexible mold, then cast concrete/plaster into it (dropping in the inner core to hollow the pour) and flex it out. Best for straight-walled, cylinder-ish pots. Test print the yoke first to check the fit on your printer.