The AAFM Series is a strong Aluminum housing with a Polyvinyl foam element that makes this muffler completely non-corrosive. The Polyvinyl insert is easily replaced so you don’t have to replace the entire Muffler. Also, these mufflers have male NPT threads of 1/8", 1/4", 3/8", 1/2" and. 1". The maximum operating pressure is 130 psi, the temperature range is 41ºF to 140ºF and it is recommended for use with air.