GAMBER JOHNSON 12 Locking Slide Arm. Mounts on any upper tube, complete pole, low profile brackets or flat surface. Locks every 22.5 degrees. Narrative: Gamber-Johnson 12 Locking Slide Arm. The entire arm can rotate around 360 degrees with locking points at every 22.5 degrees. Description: 12 Locking Slide Arm. Locks every 22.5 degrees. Swivels 60 degrees right and left. Slides 4 back and forth and tilts 30 degrees forward and backward.