See the below file for maintenance procedures and information for the CPS-20M, CPS-20M-HC20, and CPS-20M-P3K for the 6270A and 2271A pressure controllers.
This same information was added to the updated 6270A Service Manual in May 2018. The Service Manual shows the part numbers also.
See this article for CPS-20M Test Port o-rings, CPS-20M Test Port O-Rings
Note that a much quieter muffler is available to replace the original small metal filter. If you have a CPS-20M with the original metal filter,contact Pressure Calibration Technical Support by the link below, Submit a request
Below is a view of the assembled screen retainer and filter manifold assembly, and then with the coalescing (paper) filter and its retainer also. Note the placement of the o-rings.