The wera 851 series bi torsion extra hard phillips bits for use with all combi and drill drivers for impact tools use impaktor bits bi torsion extra hard bth bits significantly extend service life ideal for use with screws into general construction materials and timbers use with wera bi torsion rapidaptor bit holder for ultimate service life 14in hexagon drive 25mm bits wera screwdriver bits are designed for tough applications found in both trade and industry strictly controlled manufacturing pr