If you are into small arms history, you must have heard of SPR (Special Purpose Rifle.)
The SPR, used by Special Operations Forces of both the U.S. Army and U.S. Navy, is a heavily modified light sniper/designated marksman variation of the AR-15/M16 line of infantry weapons, and is chambered for NATO standard 5.56×45mm ammunition.
The first SPR adopted famous PRI Gen I and Gen II carbon-fiber free-float handguard.
One very important feature of PRI handguard is its carbon fiber main body. The carbon fiber can stop heat transfer from barrel to the handguard.
Now, MadBull is proudly introducing fully licensed PRI handguard rails to Airsoft industries.