Simpson 0.315 x 13-3/4" Strong-Drive SDCF TIMBER-CF ScrewModel No. SDCF221334 Coating Material. Yellow Zinc Coated Length. 13 3 4 Head Diameter (in.) 0. 59 Shank Diameter (in.) 0. 23 Drive Type. T40 6 Lobe Head Type. Flat Head with Nibs Thread Length (in.) 13 3 8 The Strong Drive SDCF Timber CF screw is a structural fastener designed for cross laminated timber construction, mass timber construction and general interior applications. These structural fasteners provide uncompromised strength for these