The Keysight X281A is a high quality coaxial-to-waveguide adapter that enables efficient conversion of WR-90 waveguides to 50 Ω coaxial lines with Type-N connector. Designed for the frequency range of 8.2 to 12.4 GHz (X-band), it provides excellent RF performance with a maximum standing wave ratio (SWR) of 1.25. The adapter features an EIA WR-90 waveguide connector with UG-135/U flange designator and is ideal for bidirectional power connections in high frequency applications where precise impedance matching between waveguide and coaxial systems is required.