Brownells Roll Spring (Pin) Holders are accurately drilled to hold tiny roll springs so perfect alignment is obtained.  The 1/16" Roll Spring (Pin) Holder is notched to clear M16/AR-15 rear sights.  The 3.5MM is excellent for holding the pin that retains the breech block on Sig handguns.  This fine set has sizes 1/16" (notched), 5/64", 3/32", 1/8", 3.5mm and each made from 5/16" Hex High Carbon 5160 Steel that is Bainite heat treated for strength.  Single groove in grip section and laser marked  for quick identification.  100% Made in the USA.