Osprey Defense Gas Piston System.
Depending on your specific AR15/M16/M4 rifle configuration, there are some major differences between tolerances and setup of the host rifle at the rifle factory. But in General, OPS-416 will fit on any AR barrel with a .750" or 3/4" diameter at the shoulder where the front sight base sits.
This is the list of handguards Osprey Defense Gas Piston System currently know will work with their system without any modifications, this list will be updated as more handguards are discovered to work with their system:
Midwest Industries 17P Rail System
Midwest Industries 20P Rail System
Surefire 500 series integrated handguard with light.
Magpul MOE Handguards with slight modification to upper heat shield
Osprey Defense Gas Piston System Installation
