RockAndSage
WKR
Midwest Industries URR - $90 TYD
If you're a bit new to building ARs, this particular design of upper receiver rod is a critical tool for proper assembly, keeping the barrel/barrel extension from over-clocking (which means your bolt lugs slip right into the barrel extension without peening against its lugs), and keeping the barrel's guide pin from breaking or damaging the slot in your upper as you torque down the barrel nut. There are a bunch of reaction rods on the market, but this is one of only a couple with the sail, which makes if far better for both safety of your parts and for precision of assembly. When you can find them in stock they're usually around $115-125. This one is brand new, never used. $90 TYD.
If you're a bit new to building ARs, this particular design of upper receiver rod is a critical tool for proper assembly, keeping the barrel/barrel extension from over-clocking (which means your bolt lugs slip right into the barrel extension without peening against its lugs), and keeping the barrel's guide pin from breaking or damaging the slot in your upper as you torque down the barrel nut. There are a bunch of reaction rods on the market, but this is one of only a couple with the sail, which makes if far better for both safety of your parts and for precision of assembly. When you can find them in stock they're usually around $115-125. This one is brand new, never used. $90 TYD.