The new AX // MP5 Lower from Aeroknox is manufactured from 7075 billet aluminum and offers AR grip compatibility. Weighing just 6 ounces there is no FFL requirement for purchase and it is fitted with no tools.
Currently only available for PTR 9 clones. Zenith clones and HK will follow.
www.aeroknox.com/product-page/ax-mp5-lower
That is hot. It would pair well with a Haga ACR stock and surefire foregrip. Just need an SP5-compatible variant
It’s not $550 hot!!
I’d stick with a Magpul lower for that price!!