The Black PEI Range of Twist & Lock Fittings is offered in ¾" and 1" CTS sizes. They have been specifically designed for Water Filtration/Softener Installs; however, they are also suitable for Marine and R.V. applications. The fittings are manufactured from high quality engineered plastic with EPDM O-rings. Speedfit Push-in system is suitable for hot and cold water plumbing applications.