A particularly handy attribute of the Herschel Wedge is its partial polarizing effect on the solar image. This permits a very convenient means of variably adjusting the image brightness, simply by using a single polarizing filter between the Herschel and the eyepiece. The filter/eyepiece combo can then be rotated and the image is variably dimmed. This method is very useful for easily achieving the optimum brightness for maximum visual contrast at any magnification.
The 1.25" version can be threaded onto an eyepiece directly. This allows you to conveniently switch between 1.25" eyepieces without removing the filter and still maintaining a close position between the eyepiece and filter. Use of a T2-15 also gives you a very convenient means of attaching and removing the Solar Continuum filter.