The MIXdrive submersible stirrer line can withstand operating conditions of -10°C up to +50°C in air or submerged. So if your application is well within these parameters, then the standard version is the appropriate fit. However, if you are operating in conditions near or higher than +50°C, then the high temperature version is for you. The high temperature version can be used in conditions up to +95°C submerged (water baths, etc.) and up to +200°C in air (ovens, etc.).
Remember that the operating conditions are determined immediately adjacent to the stirring drive (i.e., measuring temperature of environment with respect to the stirrer). Thus, although the average environment temperature might be within the appropriate range, the temperature closer to the stirring drive may be much warmer. For example, a stirring drive placed in an incubator or a water bath at or near +50°C with inadequate air flow or water circulation will actually be operating in an environment higher than +50°C.