This is Ralph Schweizer's Hacker Q80S/XS rear support/mounting kit. This rear support is adjustable in all axes and suitable for fuselage widths of approximately 12-16cm. Offset for approximately 3° side thrust.
The Aluminum bush must be glued to the carbon using Uhu Endfest 300 epoxy or equivalent.
The kit comes with carbon plates, Ttanium and Aluminium hardware along with aircraft grade ply parts to attach the support to the fuse sides. The Q80 motor pictured is not included.