The adapter is the key element however and not disposable. Oil filters are ubiquitous and very cheap.
It seems extremely effective. I’m sure there will be a new law about having an unused oil filter soon.
The filter itself is not regulated, the adapter is. In the eyes of the BATFE anything that allows you to attach a means of suppressing the muzzle report of a gun is considered a NFA item (controlled "firearm") and falls in the class of weapons such a machine guns, sawed off shotguns/rifles, destructive device (bore size over .50"), and purpose made suppressors. The later items are serialized by the manufacture and are already threaded to fit a rifle barrel (1/2" x 28 TPI is typical for .22 cal.) In addition to oil filters, plastic soda bottles have been used as "makeshift" suppressors and work reasonably well if a little water is left in the bottle to help cool the exiting gasses.
The ATF takes a dim view of home workshop inventors futzing around with anything that they might consider to "suppress" muzzle report. If you get caught with an unregistered device (no manufacturer name & address, no serial number) you WILL face felony charges, a very stiff fine and time in a Federal prison.
If you do take the time and $$$ to go through the proper procedure to acquire a suppressor (correctly fill out and file a BATFE Form 4 and provide a certified check for $200.00 to cover the excise tax.) there are still local laws to consider: CA, HI, IA, IL, MA, MN, NJ, NY, and RI ban suppressors outright.
In addition there are loads of BATFE regulations covering suppressors which you MUST follow: No one but you may use your suppressor, your buddy may not even touch it w/o committing a Federal crime, you must not take it out of your state of residence w/o telling BATFE (your newest best buddy!), if you move w/in state you must inform ATF of your new address, and the list goes on and on but you get the idea.
Regards,
GtG