Sometimes over engineering is what cost so much in such a simple principle. Drink bottle and a little water and wadding works in a pinch and is disposable and don't have to pay tax stamp and high price for it.
and the feds want a $200 tax stamp, paid and a form filled out and approved , before you assemble the adapter on your firearm
they don,t give a crap about your hearing loss they just want their money..... btw check local laws theres a few states that throw a shit tizzy if you buy a
suppressor