Really? If all that required is drilling 6-8 holes.......that's a silencer.
Depends on how it's marketed & sold. If it's marketed as a silencer kit, it's illegal, the parts being designed and intended for use in a firearm silencer. If it's a barrel shroud, solvent trap or filter, then it has other purposes, only becomes a silencer if converted into such.
There's a whole cottage industry for solvent traps, many players. Diversified Machine, SPC, Maverick Precision, Quell Tech, Quiet Bore, Hawk Innovative Tech, others. Some of them sell all the parts individually, some have kits with cones inside. As long as they are sold with a legitimate purpose other than being a firearm silencer and are not able to pass bullets through them, there's no problem, even if 99.999999% of the people purchasing them intend to convert them into silencers.
I make solvent traps to order in any diameter & length a customer wants
Now, the ones I manufacture don't have anything in them, but that's only because I have no interest in making blind cups/cones all day on manual machines.
Also, as I mentioned on the previous page, ATF doesn't care about the presence or absence of internal parts; what defines a silencer to them is that it was designed or redesigned for that purpose, and can be attached to the muzzle of a firearm to diminish the report, no matter how much or little, or if it even survives actual use.
What they have done with these policies, though, in creating a situation where the mere boring of the front cap on a solvent trap or other tube type implement that can attach to a muzzle qualifies as a silencer, is to also make it such that a form 1 maker doesn't have to do a whole lot themselves to have a form 1 silencer. Literally, all they have to do is bore that front cap after receiving their approved Form 1, and then it can be serviced just like any other, including recoring. And that's what so much of my day-to-day activity is; building cores for registered F1 silencers. Nobody is trying to circumvent any laws with this avenue, though, simply take advantage of the much faster approvals on eforms for F1. A F4 transfer is still 10-14 months, but they can file a form 1, have it approved in 4-6 weeks, poke the hole in their trap/filter/whatever, send it to me and have a professionally cored & enamel finished silencer with a warranty in another 6-8 weeks for about the same amount they'd pay on a production unit. As long as we reuse the original primary tube and don't change length or caliber, everything else is on the table.
These are some examples of recores done on the traps in the top image above after the F1 maker converted them by drilling the caps and sent them in for recore. The original primary tube section, the rear piece made of 17-4 stainless which bears the engraving, is retained. The forward section is discarded and replaced with a fully welded baffle stack. After heat treat but before applying moly resin:
A pair of the shorter ones belonging to the same customer before welding & heat treating
There have been a number of solvent trap & filter makers that did get in hot water with ATF, but in every case I know of, it wasn't the advertised product that caused them to be raided.