The SM2A12 thread-to-thread adapter contains an internal SM2 (2.035"-40) thread and an external SM30 (M30.5 x 0.5) thread. Made of anodized aluminum, it is machined with the two threads connected by a flange and can be placed at the end of a threaded tube. It is typically used to step up or down in lens tube size. The unpackaged weight of this adapter is 8.62 g.