Aluminum Cam & Groove Fitting C400 with rubber seals.
I know very little about this product, but from research, C400 seems to be a standard size. I’ll include my observation on these here….Male side is 4” across (and slightly smaller opening) and Female side is 5 3/8” (roughly) inside opening is 4 3/4
There are 2 for sale, discount if you buy two.