Milton 1/4" MNPT speed control exhaust muffler provides unlimited capability of controlling air flow at safe and reduced sound levels on exhaust ports of air valves. Complete operating safety. 40 micron, sintered bronze sleeve is held securely and protected via integrated shroud. 1/2" hex shape These units offer a combination of small size and greatest possible sound deadening qualities to reduce exhaust noise to acceptable levels within OSHA noise requirements. Specification: - Max Adjustable SCFM: 30 - Max Temp: 35F to 300F - 40 micron brass sintered - 9/16” Hex - 1/4” MNPT

Bought these off Amazon, my loss is your gain - 

B08R5X1P6G is the ASIN on amazon, MSRP - $167

BOX OF 25