The RAM-B-176-GOP1U consists of a fork stem base, double socket arm and 1" diameter ball with custom GoPro® Hero adapter. The GoPro® Hero adapter attaches directly to the under-side of the camera, replacing the factory mounting bracket. This part is designed to fit into the cylindrical bore wall of fork stems and will work with stems that measure from 12 - 33mm (.5” – 1.29”).