Park Tool QTH-1 Quick Change Bit Driver Set 8 bits. The QTH-1 is an ergonomic T-handled bit driver equipped with eight common bits to fit a wide variety of fasteners and fittings found on bicycles. The magnetic quick-change” handle allows for one-handed operation and makes changing bits quick and easy. The bit holder can be magnetically attached to any magnetic surface such as a repair stand or tool box or can be permanently mounted to any wall or tool board. The QTH-1 is a professional-grade tool built to withstand the rigors of daily shop use and is fully rebuildable.