Ultem bit driver The Ultem Pen Driver belongs in every Technician’s pocket. We give you four standard bits, but you can replace them with your mission specific bits. Material/Finish: Ultem. Note: While Ultem tools are well known for being light-weight, corrosion resistant and having a low magnetic signature, this tool uses a a strong neodymium magnet to secure the 1/4″ hex bit in place.