The design uses two identical motor mounts, which means that they both have inter-stage couplers integrated. The mount itself is a standard phenolic tube and Aeropack motor retainer.
The novel aspect of this design is the use of a 3D printed part that acts as a fin-aligner and inter-stage mount. The 3D printed tail-cone is lined with a phenolic airframe tube that provides heat protection for the 3D printed part and also provides a surface for the booster stage to attach to.
