The RAP-B-379U-252025 consists of a 1" diameter rubber ball, connected to a 1/4"-20 X 0.25" male threaded post. The male thread matches most standard camera and camcorder female threads found on the bottom of the camera. This ball base is a durable way to secure cameras using the RAM Mounts ball and socket system.
RAP-B-379U-252050 features a longer 1/4"-20 X 0.5" male threaded post.
RAP-B-379U-M616 consists of a 1" diameter rubber ball, connected to a M6x1.0 x 6mm male threaded post.
RAP-B-379U-M81208 features a larger M8x1.25 x 8mm male threaded post.