The M4 Block II is the SOCOM-upgraded M4A1 with a Daniel Defense RIS II quad-rail handguard, SOPMOD accessory suite, ACOG optic, PEQ-15 laser, and other kit. Represents the fully-kitted M4A1 as fielded by tier-one special operations units. Type: Semi-Auto Rifle Action: Gas-Operated Caliber: 5.56x45mm Capacity: 30 Year introduced: 2003, USA Weight: 7.5 oz Overall length: 32" Status: Active Military use: Yes Intended use: Military, Special Operations