They are easy enough to make and I don’t even need to register them.
You can buy the thread adapter on ebay or amazon, and use a discarded oil filter, and poof, I have a suppressor.
No need for all of these expensive devices, registrations etc. I can keep the Oil filter available for it’s intended use, and keep the thread adapter in my tool box.
Sorry, but you do need to register anything before you even start that project.....and pay the $200 tax stamp.
Unless you like $250,000 fines for a cheap oil filter.