Silica gel belongs to the rubber class, molding process is vulcanization molding. Silicone mold is up and down open mold, a piece of silicone raw materials cut, placed in the mold, heating and pressure to make products. General plastic products will have a rubber mouth, in the product after the injection to trim, the poor trim will affect the appearance. and silica gel is not into the mouth, but around a circle of burrs to repair. If the mold is very rubbish, this circle of burrs will be more obvious, like the dog gnawing.