Simpson 3/4" x 21" Quad Head SDS-Max Drill Bit, Carbide MDMX07521QModel No. MDMX07521Q Shank Type. SDS max Shank Head Type. Quad Head4x Drill Bit Diameter (in.) 3 4 Drilling Depth. 17 Length (in.) 21 Pack Qty. 1 Simpson's carbide tipped drill bits are premium quality, professional grade tools manufactured in Germany to the highest industry standards for Simpson Strong Tie. They are designed to meet precise tolerance requirements and incorporate proprietary features that enhance durability and drilling speed, while