I won't lie I do not know a whole lot about the technical side of bikes. I have a ~2000 Raleigh M80 that has been in the basement for 4 or 5 years and the Derailleur and cogs have rusted and I would like to replace them, along with the chain. How do I know what too look for when buying one, such as sizes, etc. or whatever else I need to know. I want to make sure it will be compatible with my bike. Any help would be greatly appreciated. Thanks!!