Those plastic cased stihls in 029 039 290 310 390 very common for those muffler to come apart.
Always replacing them.
Went to aftermarket ones to try on guys saws with permission and they seem to hold up better on some.
Plus I give them a cheap free muffler mod which is good for 18-23% on those choked down mufflers.
Locals hate flip caps on their stihls.
Just was designed wrong by stihl. Should have done screw in flip caps like husky did.
I replace them with these for them.
Always replacing them.
Went to aftermarket ones to try on guys saws with permission and they seem to hold up better on some.
Plus I give them a cheap free muffler mod which is good for 18-23% on those choked down mufflers.
Locals hate flip caps on their stihls.
Just was designed wrong by stihl. Should have done screw in flip caps like husky did.
I replace them with these for them.