comments:
DigitalNinjaX posted on r/airsoft1w
No they are just thin pieces of aluminum that go inside and between your barrel and your outer barrel. The only difficulty is if you may have to pick just the right thickness and amount to get the holes to line up right. You may need a big wrench or possibly even a barrel nut wrench to do it. All depends. Here are the shims. https://a.co/d/0bA3XGN3