Hi, cause my ca. 15 years old Lense cracked finaly (the inside one) so i had to think about ... !?!?!? Cause i got a free bad lense one from a friend i thought using her much stronger front lense to build a much more lifetime, stability etc. inside lense out of !!! As seal i used is a line which you use to hang on wet clothes, i only removed the wire from inside for more flexibility but i go Change this cause she´s red, as soon i found some black well Fitting hose, foam etc. for this Job !!! Cause the D.I.Y. inside lense fits very well, so the ends(sides) of the inside lense will get pushed Forward by the Frame against the seal.