#4978436
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I used a 1 3/8 inch.

AKIHISA 12 Pack 1-3/8in Stainless steel-304 Cable Clamps,Pipe Fittings & Accessories,Rubber Cushioned Insulated Clamps,Pipe Clamp,Metal Clamp,Wire Cor https://www.amazon.com/dp/B08CSRZVYH/re ... FTppniYiQc

Seems to fit well. Somewhere between the 1.25" and 1.5" I'd heard different people argue in favor of. It's a good fit.
#4978444
Zooming in and slightly enhancing one of the photos taken by Adam Savage, I believe I can clearly see 25" stamped on the clamp , it's hard to make out what is written before it though, so it could be 1/2 5" but that makes less sense than say 1.25"

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