The STD-15 Model A is a carbine-length, direct-gas-impingement self-loading rifle, available in either left- or right-hand configurations, that feature an M4 barrel, nitride bolt carrier group, and a delta-ring and clamshell-style handguard that has M-Lok slots. The front gas block contains a section of rail, and the stock adjusts to six positions. Price: $1,049 (left hand), $999 (right hand). Contact: Standard Manufacturing Co. LLC; (860) 225-6581; stdgun.com.