... reduce the noise device.We have types of muffters,about 4",6",8"and12".Welcome to your inquiry. Product informationRemarksProduct ... name Efficient Duct mufflersize 4" miniDuct mufflerFine structure ,Practical, Strong,Appearance perfectMaterials1.Up ... +carton2.Helpful for long distance transport and storage. 4 inch mini Efficient duct muffler