If you’ve got a too-long barrel thread on, say, an AR15 .22lr conversion, or one of the Savage .22lr barrels that are threaded to 5.56mm specs, you need a spacer that will prevent the suppressor from screwing on too far (which leaves exposed threads of the barrel sticking into the blast chamber of the suppressor – you’ll have carbon and lead gumming up the exposed threads, making it hard to unscrew the can, not to mention the crown will be closer than it should be to the blast baffle which isn’t good).
This precision-made spacer is a significantly better solution than a giant stack of peel washers – it has nice, parallel sides for the suppressor to snug up against, is threaded so – unlike washers – it won’t come loose when you remove the suppressor.
Works with most any suppressor / barrel combo that are threaded 1/2-28.
(Most .22lr suppressors are threaded .400″ deep, most .22lr barrels SHOULD be threaded the same to match – but some manufacturers use the longer (as much as .625″) male threads on their barrels. This will easily fill the gap and provide a secure mounting face to for the silencer to tighten up against.