Two different positive molds for casting silicone to create 3D cultured micromass cultures.  These require high rez printing.  I used a 3D printing service and had printing done at 20- 25um resolution.  To cast silicone, first coat mold with release agent.  If you use sylgard, you must degas or the bubbles will ruin the microwells.  Once the silicone is cured, I used a sharpened corkbore to punch out the silicone to the 12 well size and used 3D printed retainers to hold the silicone microwells in place.  The third file is the 12 well retainer rings.  The rings are cut (radially) using a band saw or hacksaw.  Then they can be compressed slightly and inserted into the 12 well plate where they are held by outward pressure.  The rings fit over the punched silicone to create the surface.  If the silicone is transparent, it is easy to monitor cell growth with a dissecting scope or inverted scope.