@stagstalker it does look like a single stack box due to the feed lips in the front of the box and also the flat follower by the looks of things? it maybe this wyatt box below:
https://wyattsoutdoor.com/product/cfe-5-kit/
I have always used the wyatts extended mag box but with the windows cut in like this kit below as i hate single stack box's and not being able to top load.
https://wyattsoutdoor.com/product/mbe-4-kit/
Normally you get 2 and sometimes three depending on the depth of the stock and also the type of BDL used etc.
Cheers
Bookmarks