These are copper exhaust locknuts that will not vibrate loose. Use these on all attachments that are through bolts on the exhaust system. It is best not to use these on the studs directly attached to the cylinder heads as they have more likelihood of pulling the studs out with them if you ever need to loosen them. They are great for all through bolts for the rest of the exhaust system. These are used with flat washers, whereas the regular nuts are used with wavy washers.

Ref ID: 11621711954