The Leviathan - V3 optical is one of the most advanced ETU (electronic trigger unit) on the market. It has all optical sensors for better handling and durability. Built-in wireless communication for quick setup using iOS or Android smartphones! Foam on the trigger makes great hair trigger mode. Unique Real feel trigger system (RFTS), spring simulates trigger resistance like in the real AK74. It adds secondary resistance with release after the fire. RFTS was designed by professional gunsmith for more realistic feel from shooting.