Tungsten Carbide Needle Holder Inserts Serrations is a world leader in the field of tungsten carbide needle holder inserts used in the manufacture and repair of needle holders and tweezers. We have been serving the needs of our customers for over fifteen years and we are proud to count many leading instrument manufacturers and repairers from around the world amongst our large customer base. We put this success down to making quality our number one priority and providing a flexibility that enables us to respond to the different needs of manufacturers and repairers.