These are lower receivers for the DB Alloy that are compatible with the metal fire control group reinforcement plates found here: https://odysee.com/@db-firearms:4/DBs-FCG-Reinforcement-Dev-Pack-V1:4 These plates should help solve the most common FCG issues with 3d printed receivers using AR-15 hammer, trigger, safety selector. For full documentation on the DB Alloy, please refer to the original DB Alloy download on Odysee HERE: https://odysee.com/@db-firearms:4/DB-Alloy-Official-Release-1.0:4 LBRY Tags: 3d printing; alloy; db alloy; sten; mac