idf nagmachon please help

[FullArmor]

Are these exhaust or not? Is this somekind of flappervalve or straight pipe? Please help!

[Martinnfb]

Flaps, but often removed .

[dodgem37]

Exhaust valve.  As also seen on tractor-trailers.

              

Sincerely,                                                                                                                                                                                                                                                    Mark

[FullArmor]

Thank you all👍.  Now i must replicate those somehow...maybe using thin aluminum or copper.