The interior on the "U" part of the clamp measured about 1.5" that goes over the factory bar. The interior that the rigid conduit goes into - measured a hair bigger than 1 3/8" Hope that helps some on your quest.
05 TJ RME 42RLE with some things
05 KJ CRD 545RFE, GDE Eco tune, Franky II, Al's 4.5 A-arms, JK Rubi Moabs, Silent Armors 245-70-17's, Spidertrax Adapters, Rola Basket, Fumoto Valve, Pinch welds pounded
FS or FT (2) JK Rubi 17" Moab Rims - really nice shape
Need JK Rear Spare tire bracket for project