Baffle berlubang, biasane pipa lurus kanthi bolongan cilik. Biasane digunakake ing muffler knalpot sing diarani wong minangka watesan aliran udara paling murah "silencer" utawa "inti".
Desain klasik sing ngidini energi swara sing sumunar liwat bolongan menyang kemasan sing diserep lan surem.
Jenis "inti" biasane bisa ditemokake ing Max Racing Exhaust Alur Lurus Series Glasspack resonators , Muffler & Pusat Muffler di Babak , Oval , Khusus T kothak tipe & h-box muffler.
