The RAM® X-Grip® Phone Mount with RAM® Vibe-Safe™ & U-bolt Base - Short (RAM-B-149Z-A-UN7-462) / Medium (RAM-HOL-UN7B-462) is a combination of the RAM® X-Grip® Phone Mount with Handlebar U-bolt Base and the RAM® Vibe-Safe™ - the vibration damping accessory is designed to protect electronic devices from a wide range of vibration frequencies. The RAM® X-Grip® can rotate between portrait and landscape by loosening the center screw. This product comes with one (1) short B size arm OR one (1) medium B size arm and one (1) RAM® U-bolt Base that accommodates rails from 0.5" - 1.25" in diameter and an optional device tether that is recommended for outdoor applications. The holder is compatible with handheld devices that will fit the dimensions listed below, it is important to verify the dimensions of your handheld device with a case / sleeve / skin when determining the overall size.