25mm to 17mm ball adapter material is: aluminum alloy, weight: 45g. Sturdy and durable. 1'' (25mm) ball adapter compatible with RAM mounts and any B size double socket arm. 17mm ball adapter compatible with Garmin 17mm swivel ball mounting pattern GPS mount. 25mm / 1 inch to 17mm Ball Adapter for RAM Mounts B Size Double Socket Arm Long:4" 25mm to 17mm Ball adapter widely used on 17mm swivel ball mounting bike, motorcycle phone mount holder, navigation brackets and other electronic equipment mounts. (Long:4") 25mm / 1 inch to 17mm Ball Adapter for RAM Mounts B Size Double Socket Arm, Garmin 17mm Swivel Ball Mounting Pattern GPS Mount