Trolley Wheel Replacement Kit for LightRail
 3.0, 3.5 and 4.0. This is great for DIY customers. Installation is 
super simple, and there is even a tutorial video about it on YouTube 
(URL: https://www.youtube.com/watch?v=MIbtIWyNFp0). The Trolley Wheel 
Kit comes packaged with 4 new trolley wheels and screws in a header 
labeled zip lock.