This is a MK8 toolhead for the excellent Voron Stealthburner.
VORON StealthBurner (vorondesign.com)
I've not printed the GA version, but I printed, mounted, and used the betas successfully.
It's designed for 2 additional 20mm M3 BHCS to hold the hotend in with heatset inserts in the rear piece highly recommended.
Print using Voron print specs and whatever material suits your need, I used ABS/PC blend.
The author remixed this model.