Busta,
The Hubbard's item is 5/8'' diameter, like the latter 'new' NEF Huntsmans, with a thread pitch of 18 TPI. Overall length including primer carrier is 1 5/8", breechplug alone 1 3/16".
The threaded portion is 7/8" L, with 1/8" unthreaded beyond that on the forward (combustion) end.
The earlier Hubbard's breechplug (which mine is) removes with a 1/2'' socket, and the primer holder has a knurled outer circumference for finger tightening/loosening, with a 7/64" allen-hex indent at the start of the flash-hole for when added persuasion is needed (usually).
The newer Hubbard's system requires a 7/16" socket for breechplug removal, and the primer carrier is hex shaped on it's exterior of 3/8" dimension for removal with a socket or open-end wrench...that's an improvement IMO. Otherwise, critical dimensions are the same between the two Hubbard's products.
As I don't have a NEF item at my disposal for comparison, so the possible interchangeability or adaptability is uncertain.
The Hubbard's primer holder is 1/4x28 TPI and projects 7/16" beyond the breechplug... as no plastic carrier is required for the 209 primer, if this dimension seems compatible with the NEF breechplug, this alone could be a partial retro-fit upgrade in lieu of the OEM item.
Although the plastic primer thing allows instant observation of "loaded/unloaded" condition of the rifle, no such feature exists in a centerfire arm. Since all firearms should be treated as loaded unless one has checked, that seems superfluous IMHO.