https://www.dolphmw.com/products/waveguide-air-inlet/ Dolph microwave offers a standard line of waveguide pressure inlet from WR28 to WR650 for pressurizing Waveguide systems with clean air or other gasses. Waveguide pressure inlet are available in almost all combinations of flange type and have a 1/8" NPT female inlet. We can customize waveguide pressure inlets to your specifications upon request.