These AR15 anti walk / anti rotation hammer and trigger pins are what you need to keep your receiver from excessive wear and tear. Keeping the hammer and trigger pins from rotating is especially important when shooting full auto or with pistol caliber builds, such as 9mm AR15's.
PIN SET, AR PLATFORM, HAMMER/TRIGGER, ANTI-WALK, BLACK
Trigger Upgrade Kit: Davidson Defense AR-15 3 lb Drop In Sierra Performance Trigger System + Recoil Technologies Anti-Walk AR-15 M16 Rece
KNS Precision AR-15/M16/AR10 Gen ST Non-Rotate Trigger/Hammer Pins
TITANIUM ANTI-ROTATION TRIGGER / HAMMER PIN SET
AR15 Trigger & Hammer Stainless Steel Anti-Walk Pins
AR-STONER Hammer Trigger Pin AR-15, LR-308 Matte
Strike Industries Anti-walk/Anti-rotation Trigger/Hammer Pins
AR Triggers & Anti-Rotation Trigger Pins - School of the American Rifle - AR Build Junkie
Rise Armament, Anti-Walk Trigger & Hammer Pins, AR15 & AR10 Compatible
Armaspec Anti-Walk Trigger / Hammer Pins Stainless .154 for ar-15 lower (CT35ARMASPEC136SS)
Strike Industries Anti-Walk Trigger, Hammer Pin Kit AR-15 Steel Matte
AR15 anti-walk pin set for AR-15 lower receivers
KNS Anti-Walk Hammer Trigger Pin Gen ST Non Rotating AR-15, LR-308
Airborne Arms AR Max-Diameter Titanium Anti-Walk Pins - 2 Set
RISE Armament Anti-Walk Trigger and Hammer Pins