The Strong-Drive SDCFC Timber-CFC screw (CFC — Countersunk, Fully Threaded, Cylinder Head) — a robust structural fastener available in a variety of long sizes (500 mm – 1,000 mm) — is designed for cross-laminated timber (CLT) construction, mass timber construction and general interior applications. These sturdy 0.390"-diameter structural fasteners provide extra strength for demanding applications requiring large-sized structural members. The compact cylinder head provides clean countersinking with a reduced footprint. The yellow zinc, fully-threaded screw, with a proprietary point, provides fast starts and excellent withdrawal resistance. For interior and dry applications only.