Okay, here are some additional notes and details about the Peterson breather can.
Unless you want to cut your firewall for clearance, this is the 'service position.' Undoing the 11 mm nut on the band clamp allows the can to be pulled forward, clear of the firewall. To remove the cap for servicing, loosen the 11 mm nut on top. Once it is just broken loose, unscrew the whole cap to remove. THE NUT, THE CAP, AND THE THREADED ROD ARE CONNECTED. In fact, all of the guts are connected to the threaded rod (see photo 3). Once the cap and filter are removed, oil can be removed with a turkey baster or whatever.
At the bottom of the breather can, there is a tapped bung that holds the threaded post. The bung is stitch welded to the can in a way that allows oil to flow beneath it and into a tapped drain, which is the other way to service the breather can. What you can't see...is any oil. After five days of ordinary driving and one 15 minute track session, there is not a single drop of oil in the can. I will continue to monitor the rate that oil is captured by this system.
Here you can see the end of the threaded rod that screws into the bottom of the can. There is an internal baffle, within which is a foam filter. The threaded rod also spaces the cap away from the baffle and the sides of the can, so that it does not seal and is a vented system.
Besides a better of understanding of how this breather can works, you can also see some of the reasons that this breather can might initially seem overly expensive, until you see the quality of construction and the hidden details.
Jimmy