Tennessee Arms offers the toughest Hybrid AR15 Lower on the market. Weighing in at a scant 5.6oz , you won’t find a lighter lower when it comes to toughness. Their lowers have been proven in the field with every caliber from .22 to .50 Beowulf and everywhere in between. High round counts are around the 20K round mark using 300 Blackout. They have been ran through tactical courses, they have been ran over by F250s. They have been baked at 175 for 2 hours , and frozen . You won’t find a tougher hybrid lower.