Retro A1 round front sight pin assembly

These are the parts you need for your A1 front sight base

The A1 front sight base has either a round pin or square pin, and has five notches to install in the FSB, unlike the 4 notches of the A2 sights.  The round pins are found on early Vietnam era retro rifles.  This set includes the spring and detent, which are all needed to be installed into the A1 FSB.