This spring compressor is great and the instructions were very good. Take your time and remember to only use two cylinders at a time, then find TDC on the next set and third one do it valve stem seals!
I don't usually take the time to review products unless they are awful or phenomenal. This tool is definitely the last! If you are planning to do valve or valve spring work on your Cummins 12 valve, this tool is the tool for you. Good guide, well put together and does both quills at once.