Malco - HW8X3/4 ZWG HW8X3/4ZWG Sheet Metal Screw (100 Pack), 3/4" Length, White Malco?s Zip-in Screws are known for their superior quality and is considered by many for being the best screw choice for HVAC metal duct fastening. A unique thread design and quality controlled manufacture spell the Zip-in sheet metal screw difference. Zip-in?s are made with a sophisticated heat treat process which allows the screw to taper to a fine, sharp point without sacrificing critical point strength. A single starting thread is formed down to the very tip of the point and is the source of Zip-in?s penetrating power. A second thread above the point engages after initial penetration and drills in the screw double fast. Malco?s Zip-in screws are faster driving, with a greater capacity for fastening heavier gauges of sheet metal than any other self-piercing type. For the best performance, use any Zip-in Sheet Metal Screw with a Malco C-RHEX? Cleanable, Reversible Dual Sided Hex Driver. Features Malco?s Zip-in Screws are known for their superior quality and is considered by many for being the best screw choice for HVAC metal duct fastening. For the best performance, use any Zip-in Sheet Metal Screw with a Malco C-RHEX Cleanable, Reversible Dual Sided Hex Driver. Malco?s Zip-in screws are faster driving, with a greater capacity for fastening heavier gauges of sheet metal than any other self-piercing type. USA SHIPPING estimates delivery times and we work to get your item to you as quickly as possible and within those times, but please know it may take slightly longer than the estimate.