It is model JPGS-5B.

I am hoping someone can tell me for sure...before I order one.  It looks like it is gonna be really close...

I thought I read somewhere that the DD rail has got an ID of 1.440. Do you know the OD of that gas block?
That's all I have to help but good luck as I am trying to get that rail to put on a Bushmaster ORC. It has the factory gas block that I intend to machine down to fit. Ill put this here to watch for an answer from someone who knows.
Thanks OP.

I think all of the dimensions are good.  The only part that concerns me is the lower portion where the bolts are...it looks like it might be too wide.

JP Adjustable Gas System for AR-type rifles.

?Low profile, rail-free design allows installation under hand guards.
?Material: 416 stainless
?Finish: Black oxide
?Weight: 2.25oz
?Length: 1.28"
?Height: 1.40"(overall), .775"(over bore)
?Width: .85"
?Attachment: 6-32x1/2" socket head screws, T15 Torx drive (included) (includes 5/64x5/16 roll pin for gas tube installation)
?Adjustment: 8-32x3/8" stainless set screw, 5/64 hex drive (included)

Gee, that wasn't too hard.