A CPP500 and the Borgeson 670 are pretty much the same. The CPP500 is a bit cheaper most places most times.
605 boxes are outdated, they have the wrong valving, they develop play, and they leak. If you already have it or can't afford more, that's one thing, but don't pay new box money for one, or expect much.
I think what they call a "400" box is similar to a "500" box but it's for applications other than 55-57s.
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