These 3M Hookit blocks combine the lightweight flexibility of traditional foam blocks with the dust extraction power and control of dust-free sanding blocks. The blocks flex to help easily restore contours and bodylines, while providing a firm backing for abrasives. Features 3M Hookit attachment system. They include a vacuum regulator that lets the operator adjust suction for easier block control when sanding.Enjoy the benefits of dust extraction and the firm flexibility of a foam sanding block with 3M Hookit Dust Extraction Flexible Sanding Blocks. Built for balance, these lightweight flat-faced blocks deliver a flexible but firm backing for contour and bodyline restoration. The built-in vacuum regulator lets the operator customize their perfect mix of dust-capture suction and freedom of movement. The family of blocks includes four lengths: 5 1/4 inch (133 mm), 7 inch (178 mm), 10 3/4 inch (273 mm) and 16 inch (406 mm) - plus a three-size block kit. The 3M Hookit attachment system means they're compatible with 3M Clean Sanding Abrasives, 3M Net Abrasives, and other hook-and-loop-backed abrasives.