Viega Pex Press 53507 Crimp Caliber Tool. This caliber crimp tool is used to secure PEX tubing to crimp fittings. A correct crimp tool is all you need to create reliable, long lasting connections. High grade metal is used throughout the clamp, ensuring that the seal made will last as long as you need it to without issue. This tool is designed for 3/8", 1/2", and 3/4" crimps.