The double ball adapter is connected by an aluminum alloy rod. TPU covers the ball head with anti-slip and wear-resistant properties. Widely used on bike & motorcycle phone holder, navigation brackets and other electronic equipment mounts. 1 inch ball joint compatible with RAM Mounts any B size double socket arm. 17mm ball joint suitable for 17mm swivel ball mounting pattern device mounts Brcovan 1 inch ball to 17mm ball adapter. The double ball adapter is connected by an aluminum alloy rod. TPU over-molding ball head, non-slip and wear-resistant. (Pack of two)