Retro Fitting:

Retrofit projects replace or add equipment to existing machines to improve their energy efficiency, increase their output and extend their lifespan.

The production of retrofit parts is necessary in manufacture when the design of a large assembly is changed or revised. If, after the changes have been implemented, a customer (with an old version of the product) wishes to purchase a replacement part then retrofit parts and assembling techniques will have to be used so that the revised parts will fit suitably onto the older assembly.