For the planned extremely large telescope projects not only the primary mirror diameters, but also the dimensions of the other optical components are increasing. For the involved manufacturers of astronomical filters technical issues like polishing, coating, measurement, handling and cementing are demanding. Not only the availability of monolithic glass substrates of the required dimensions is critical, but also the required glass quality regarding homogeneity, bubbles, inclusions, and striae. Additionally an individual production of such unique astronomical components is an economical risk, as it does not fit to the usual mass production of small filter components. It is the goal of this paper to call attention to this potential critical path for the future astronomical projects. The status of the filter glass production at SCHOTT and the development needs for these challenging components are discussed.