Patented split shank absorbs the stresses of insertion during placement. The split shank closes upon insertion to deliver maximum retention with minimal stress. Flexi-Post External Wrench, fitting post sizes 00 - 3. Crafted with a durable design. Facilitates the insertion of dental posts. Offers enhanced grip stability. Reduces stress when inserting posts. Flexi-Post External Wrench is a handy dental instrument that features a split shank that absorbs insertion stress when placing posts. The wrench works by closing when being inserted with reduced stress and optimum retention.Built with a solid construction, Flexi-Post External Wrench fits post sizes from # 00 to # 3.