You cannot buy these without buying the whole gun.  I got these on a special deal.  These are super accurate barrels.
I have four of these and have a ZEV and Mega Barrels Available in 308/7.62.

11" Fluted BRONZE 5.56 Threaded 1:7 Twist $345
9"   Non Fluted 300ACC STAINLESS Threaded 1:7 Twist $190
10"  Non Fluted STAINLESS ACC300 Threaded 1:7 Twist $190
10"  Non Fluted BRONZE $300 Threaded 1:7 Twist $290



Technical Specs

ZEV custom 416R 16" fluted match barrel with bronze PVD coating, chambered in 5.56 NATO with a 1:7 twist and mid-length gas system. Capable of consistent sub-MOA accuracy with high quality factory ammunition.