Great for mounting to rails, posts as well as vehicle headrests and other round rails within the listed dimensions Features: Torque bar mount with 1.5” rubber ball - Fits all RAM 1.5" ball socket arms Fits rails 3/4” to 1” in diameter. Includes hex wrench and sizing inserts for a snug fit and protection of the rail. Utilizes nylon-insert lock-nuts to prevent loosening in high vibration environments Constructed of powder coated marine grade aluminum Genuine RAM Mount: Part # RAM-408-75-1U Manufacturer's lifetime warranty Made in the USA.