Looks like the ones with the slip on top are the J-20, not sure which but the ones he has fit the big WBY base down in them.
The 50 rd H50XL boxes I also use for the Lapua cases will too, but you've got to push the cases down into the thing it's so tight, so I use the slip on boxes for my 416 too. My slip on top 20 round boxes are from J&J Products though (45-70 to 600 Nitro).
The 22 rounds MTM RF22 cases are nicer than the slip on J&J, so I'll be switching. I hate the tops slipping off and spillin ammo! [img]images/icons/grin.gif[/img]
I've got a couple of the buff 10-70 cases too, nice for the pack, saddlebags etc, and they don't "rattle" either. They allow for a 4.075" max OAL in case you wondered.
Here's an interesting option...