The Self-Drilling Square Drive Screw 4.2 x 13mm, is the most efficient method for installing rectangular and spiral ductwork. This high-quality steel-to-steel application screw, is the fastest option available. The SQ2 Drive Compatibility ensures a secure fit, saving time and effort during installation. This high-quality screw also removes excess material upon installation, ensuring a perfect fit every time. Choose the Ductflange Self-Drilling Square Drive Screw for a time-efficient and reliable installation solution.