This is an adjustable 48 mm extension tube that adds 8-12 mm of length. Thread is the standard 2" filter thread size of M48 X .75. The depth of the male thread is 9.5 mm and there is a thin (1.52 mm) threaded locking ring on this thread to adjust the spacing. The femail thread is 4.95 mm deep. The body is 2" in outside diameter.