These chassi blocks were made to replace the affected hornby class 50 models that suffer from mazak rot commonly known as zinc pest. the diecast peice that is below the cab on both ends is prone to suffer fro mazak rot in some models. This manufactured part is to replace the entire peice. It also has the same tabs where the LED fitted light board sits.
 
Pack of 2
 
Very easy to use and durable.
 
Most common affected models that this chassi block will replace are:
R2785
R2880
R2248