Wheelchair Rail - Tube Mount with Extension & Tablet Holder for Amazon Kindle Fire. (sku 21675)Wheelchair Rail and Tube Mount with Extension and Tablet Holder for Amazon Kindle Fire. This Mount features a U Bolt with 1. 5" Rubber Ball, a Standard Double Socket Arm 1. 5", a Double 1. 5" Ball Adapter, a Double Socket Swivel Arm with hinge for 1. 5" Ball to 1" Ball together with a Universal sprung loaded Tablet Holder. With four points of rubberized 360 degree rotation and a connecting central pivot hinge joint that rotates forward and back 180