The Xeno Flash Hider and Adapter mate together with left-handed threads, eliminating your worries of the adapter unthreading from your silencer when removed. This also lets you verify your mount is still tight when installing on your firearm.
 

6310XE is 2.157" long, and has a pin hole for pinning it to a barrel.  Assuming 0.5" of threads on the barrel for muzzle devices, 6310XE will add 1.657" to the barrel, and bring a 14.5" barrel to over 16.1".  A pin hole is drilled on the bottom for pinning 6310XE to the barrel.