Brooks Model 1390 Filter is designed to be used with Brooks flowmeters, flow controllers and NRSTM needle valves. Both male and female ends of this filter are 5/16"-24 threads. 

The connection fitting supplied with the Brooks equipment is removed, the filter is screwed into its place and then the original connection fitting is attached to the female end of the filter.

Model 1391 Filter is identical to the Model 1390 except that it has a 1/8" (3.17 mm) NPT connection at the male end. It is intended for use with the standard adapter found on a Sho-RateTM flowmeter and is screwed directly into the adapter. It may also be used in any 1/8" (3.17 mm) NPT female cavity.