AEROSIL® products provide a set of properties in silicone rubber and sealants. To adjust the rheological properties of RTV-1C silicone sealants, RTV-2C- and liquid silicone rubber (LSR/LIMS), a variety of different AEROSIL® grades with specific functionality are available. Reinforcement and heat stability are often very important for a multitude of applications of HTV/HCR and LSR silicone rubber. By using fumed oxides, those properties can be enhanced. Only due to these AEROSIL® products can the final silicone rubber products achieve the desired properties. In addition to the above mentioned effects, optical properties of the final silicone rubber products are as important. For many applications, e.g. medical devices, electronic and sports goods, and structural glazing, a high transparency is requested by the end user. Standard AEROSIL® grades with high surface areas already offer an acceptable degree of optical properties. However, for Evonik Degussa's researchers, the target was to provide an AEROSIL® fumed oxide providing excellent optical properties, especially for super transparent applications. Therefore, we developed a special production process which enables us to adjust the structure of the AEROSIL® fine particles, resulting in outstanding transparencies in silicone rubber systems.