Review on High-Quality Prime Line 9187527 Slotted Spring 25 Pack for Ultimate Versatility and Durability by Brad Schillings

This is the roll pin needed to install the latch retainer on the bottom of the AR receiver. Other uses, I'm sure, but that's all I care about. This is the type of part that can easily fall off and get lost during assembly, so extra accessories are a good idea. The price is good.