CaffeL demonstrates a 3D printed shell ejecting kit that converts the Action Army AAP-01 GBB pistol into an AK-style carbine. While its signature feature is shell ejection, the kit is designed to function as a regular carbine conversion even without the shells installed, making shell ejection an optional feature. For external attachments, the outer barrel is equipped with a 14mm CCW thread, allowing the use of various accessories via an adapter. It's important to note that due to the specific design of the shell ejection system, the kit only accepts printed shells, and brass shells are not usable.