This is my version of a insulated rail joiner for model train track (HO or OO scale). As the joiner is very small a 0.2 nozzle should be used. Printing with a 0.4 nozzle can work but often fails and the small tolerances can lack strength. It prints well in both PLA (yellow print) and PETG (green print). In the picture with the GREEN joiner you can see how it compares with a commercial joiner (transparent) on the other rail. As far as I am aware all commercial joiners are transparent but you can print this model in any available color. I hope you find this model useful.