Scottys139 Phone Holderoffers a phone holder that is legitimately marine-grade. Varying temperatures, constant UV exposure, and saltwater is no match for the engineering-grade materials that Scotty is famous for. Strength, durability, and longevity. Our phone holder is made to withstand heavy use in harsh environments.Positioning and securing your device has never been more effortless and reliable with an easy grip knob that allows for width adjustments securing devices between 2 and 3 wide.Another feature is the opening below for access for charging your device while in use. Includes, post, track and rail mount–1Compatible with devices and smart phones between 2 3 wideDual ball-joints provide infinite flexibility for positioningPost Mount fits all Scotty post mounting optionsEasy Grip T Knob