The popular Axe platform was revamped into this new version in October 2014. This newer "Axe Pro" shouldn't be confused with the pre-2015 Axe Pro classic markers which were sold by ANSgear (they were stock Axe markers equipped with a Redline upgraded foregrip). The newer Axe pro marker is a redesigned platform, so most of its internals are no longer compatible with the earlier Minis and Axes.
Main Enhancements from classic Axe to Axe Pro:
Redesigned regulator mounting method
Empire accessory feedneck standard (note: the body still has feedneck threads)
Shorter body profile
Removeable eye covers; wired eye harness
Rubber detent "nubbins"
The following parts are identical between classic Mini, Axe, and Mini-GS:
Top air transfer tube
The ASA regulator is identical to that of the Mini-GS, but different compared to the classic Mini and Axe.
Empire markers use a mixture of both metric and 1/16" AS-standard o-rings. Sometimes you can swap one for the other, but it often requires experimentation because the new o-ring will have a looser or tighter fit compared to the factory o-ring. For instance, the firing poppet's o-ring can be swapped with a 13/90 instead of the factory 2x10-mm ID o-ring.