PLEASE READ FULL DESCRIPTION
This cage and foam ring will fit the CS-400 if you cut a hole in the top cover.
This will also fit 490/4910/501P chainsaws, IF you purchase the CS-400 intake elbow and the filter "CAP"
You will also need to cut a hole in the actual air filter cover or run without the air filter cover.
Part numbers for the CS-400 parts needed to use this cage and foam rings :
Air Filter Cap
These 2 items can be purchased from www.sawagain.com
Just do a search on the saw again website and type in those part numbers.