The RAM® X-Grip® Large Phone Mount with Twist-Lock™ Suction Cup (RAM-B-166-UN10U) comes with everything needed to secure a phone to a windshield. This bundle includes the RAM® Twist-Lock™ base, medium-length double socket arm, and universal spring-loaded X-Grip®. The RAM® Twist-Lock™  suction cup is 3.3" in diameter and is designed to have a strong hold on glass and non-porous plastic surfaces, including RAM® adhesive disks. The spring-loaded RAM® X-Grip® phone holder allows for a perfect custom fit across phone models and small electronic devices through expansion and contraction of the arms. The holder features four grip knobs that attach to the arms for a secure hold; also included is a rubber device tether recommended for outdoor & high vibration applications. To ensure fit within the RAM® X-Grip®, it is important to verify the dimensions of the handheld device while within its case/sleeve/skin. The patented rubber ball and socket system with adjustment points at both ends of the socket arm allows adjustment to the optimum viewing position.