Our handy, compact tool is uniquely designed to combine several tools into one. It has a spanner wrench that fits the receiver extension castle nut on M4-style collapsible buttstocks, with interchangeable pins to fit nuts with both old (round) and new (square) teeth, so you're ready for whatever type of nut is on the gun in front of you. Pins for both styles are included and easily changed by loosening a hex screw in the tool. For fixed rifle buttstocks, there's a screwdriver blade to remove the buttplate screws and a wrench for the nut on the receiver extension (buffer) tube. There's even a ½" square opening for a torque wrench, and even a hole for hanging the too Mfg: Brownells SPECS: Round - Stainless steel, silver finish. .124" (3mm) diameter. Square - Steel, blue finish. .164" (4mm). Available in 3-Paks.