Keeps your Brownells Buttstock Tool functioning like new. Helps keep the edges of the receiver extension nut slots undamaged, and lessens the chance of marring the metal. Square fits the newer, M4 style collapsible buttstock receiver extension nuts with .164" wide, square engagement slots. Round fits the older style collapsible buttstock extension nuts with 1/8" diameter, round pin engagement recesses.
AR-15, Issue:09, Page:074
Big Book Catalog, Issue:66, Page:072
Law Enforcement / Police Store, Issue:08, Page:053
New Product Supplement, Issue:593, Page:017
SPECS: Round - Stainless steel, silver finish. .124” (3mm) diameter. Square - Steel, blue finish. .164” (4mm). Available in 3-Paks.