Is NEMA 3R Wireway available in sections rather than complete units?

[Installer]

Is NEMA 3R Wireway available in sections rather than complete units?
I hope to make a twenty foot run with continuous sections that screw together.
All I can find are individual closed end units like shown below

 

[farmantenna]

my 30" Google search shows connectable units. I examined Eaton cat but looks just like Milbank, probably same exact items.