The Firearm Blog goes over the SIG-Sauer M400 X-Series SDI, which is sorta the SIG Sauer SPEAR AR according to them... "In this episode of TFBTV, Hop checks out the new SIG-Sauer M400 X-Series SDI. Don’t let the awful, terrible, truly indefensibly bad name fool you, the X-Series SDI is actually pretty cool. This AR adopts some of the improvements of SIG’s Spear LT rifle and is more full-featured than the older M400 Tread series rifles. But it also costs way more, so it really ought to be."