Threaded for your 5.56mm carbine.
Machined from 4150 steel.
Phosphate coated per MIL-STD-171.
Predrilled hole at the base for permanent installation.
When mounted per BATF specifications for a permanent installation it will bring your 14.5" M4 barrel to a non-NFA length of over 16.1".
The A2X is predrilled and comes with a dowel pin and crush washer for installation.