This is a Spike's Tactical AR known as the ST-15 chambered in 223 Remington, model STR5035-MLS.
Spike's complete rifles are built to strict standards" inspected by their professionally trained armorers" then test fired for final functions check.
Features:
7075 T6 Construction
Mil-Spec Phosphate Coated Barrel
Phosphate Coated M16 Complete BCG