Designs Our released designs are listed here. Click on any of them for a detailed page with links to the download. SL-15 AR-15 Lower Receiver SL-9 AR-9 Lower Receiver. Stock System 3D Printed Fixed Stock System. ORCA-15 Orca 3D printed AR-15. SL-308 LR-308 Super Lower SL-15-DR Double Rib AR-15 Super Lower. Grip System 3D printable AR pistol grip system. HCC TPU Hose Clamp Cover Super Safety Active Trigger System