? EASY TO INSTALL: After select and fit the correct spacer, install the ball base. Step 1, insert the ball base into the motorcycle fork stem tube. Step 2, use the Allen wrench included with the package to tighten the bolt of the ball base clockwise. Installation Complete. ? PRE-INSTALL CHECK: Measure tube diameter, select and fit the correct spacer before installing the ball base. Support minimum tube depth 38mm. ? The motorcycle fork stem ball base included B size 1" TPU ball allows for connection to RAM Mounts & BRCOVAN any B size 1 inch ball double socket arm. Work for other devices with 1 inch swivel ball mounting pattern. Great for motorcycle phone mounts, tablet mounts, navigation device mounts, rod holders and much more in a wide variety of applications. ? Package comes with two sizes spacers. Small size spacer fit for tube 12mm to 18.5mm in diameter, Large size spacer fit for tube 18.5mm to 25.4mm in diameter. You can choose one size of the spacers according to the tube diameter for installation. It is not supported to use two spacers of different size at the same time. ? The ball base designed to fit into the cylindrical or hexagonal bore wall of motorcycle fork stems. Suitable for tube diameter 12mm to 25.4mm.