This bridge comes with 8 separate stl. files with 4 in each 00 gauge and N gauge. The bridge comes in two halves with pieces for the light and block the light fits to. Each of the lights can fit a single 3mm LED.
 
For those modelling in TT:120 the N gauge model can be scaled by 125% and those modelling in 3mm can scale the 00 gauge model by 75%.