WR-90 Flat Flange to WR-112 Choke Flange 5-1/8" lg Waveguide Transition Adapter | eBay
Waveguide Sizes | Dimensions & Cutoff Frequency - everything RF
RF Modules 8.2 to 12.5GHz Waveguide with WR90 Flange to coaxial Adapter Right Angle 90 - AliExpress
Types of Flanges
WR90 Waveguide to Coaxial Adapter, 8.2 to 12.4GHz, PBR Flange
Wr90 X Band 8.2 to 12.5GHz Waveguide to Coaxial Adapter with Wr90 (BJ100) Flange to SMA-Female - China Waveguide to Coaxial Adapter, Wr90 | Made-in-China.com