This is a direct replacement for the on/off switch that will fit many microscopes.  We have identified that it will fit the Nikon Labophot 2, Optiphot 2, E100, E200, E400, E600, E800, E1000, 50i, 55i, CiL, Ni, TS100, and many more.  This switch also fits other brands.  Measure the swith before purchasing as manufacturers sometimes change products.  The dimensions are 15mm x 21mm x 21mm.  The photo doesn't show but the switch has a red lighted face.