This is what 2A Armament says:
This 2A Armament AR 22LR complete upper makes a perfect complete rifle when paired with any 2A Armament AR15 lower receiver or any other mil-spec AR15 lower receiver. This complete upper makes switching from 5.56 to 22LR too easy. This is achieved by simply breaking down the rifle and changing out uppers. This lightweight complete AR 22LR upper weighs in at only 2 pounds 4 ounces. This complete upper has many of the features that you have come to know and love in 2A Armament products.
2A BALIOS LITE GEN 2 UPPER RECEIVER - CNC machined 7075-T6 billet "slick side" mil-spec port door, retained port door rod, M-4 feed ramps, machined indexing marks
2A 22LR BOLT-Grade 5 6AL-4V titanium bolt, stainless steel barrel collar, and high-quality Polymer buffer (patent pending)
2A 22LR FLUTED BARREL - 16.5",7075-T6 Billet aluminum barrel, rifled 4140 steel insert,1:16 Twist,1/2x28 thread
2A THREAD PROTECTOR - hard anodized aluminum
2A HANDGUARD - 2A Armament 12" 6061 extruded Aethon or BL G2-RAIL, MLOK, aluminum barrel nut.
CHARGING HANDLE: BCM-mod4
WEIGHT - 2 lbs 4 oz
Product of the Great State of Idaho, MADE IN THE U.S.A.