They are very reliable and with lubrication, will run forever. They were manufactured with e-units and without. The only difference was price. Essentially, there were two models, a Birney and a Brill. The Brill double truck model was more expensive. If you get one without an e-unit, they are easy to install. I have been running two of them on a point to point layout for years. Though no longer available, I installed a Pocono Mountain Lines electronic system that allows for stop & go and reverse operation. There are other systems that operate in a similar fashion that are available.