IWI Zion Z-15 5.56 NATO 18" 30 Round Semi-Auto AR15 Rifle | Black The Zion-15 18" Special Purpose Rifle (SPR) takes inspiration from the MK12 while receiving a contemporary makeover. This updated version features a 17" Free Float Handguard with an integrated ARCA Rail, a sturdy steel barrel nut, a B5 Systems Stock and Grip, an IWI 2-Stage Precision Match Trigger, and comes complete with a 30-round Magpul PMAG.