We were offering RTV molding before it became cool.
Silicone can't be 3D printed. We use 3D printing to create the molds that we pour silicone into. This makes quick test fits and demonstrative silicone pieces faster and cheaper than milling mold. Surface finish does suffer due to the layer heights of the 3D printed mold but for test fit before moving to final production (at US based Extreme Molding perhaps?) these molds do the trick.