Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2846469.
you place the plastic soda bottle into the smallest innermost ring, then screw on the cap till tight. then fill the soda bottle with water . then fill the glass with water up near to the cap. then place the ring with soda bottle on glass., quickly so as not to spill the water. then you place your avocado pit down into the ring center. when the water level goes down the water will come out the soda bottle into the glass and stop at the same level. you never have to worry bout filling the water again. except when the soda bottle is empty.
i added a ring (v6) where there are 4 holes to fit up to 4 bottles. up to 4 times the water filling capacity. just need to print more caps.