The SM1A24 thread-to-thread adapter contains an internal M25.5 x 0.5 thread and an external SM1 (1.035"-40) 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 attach an M25.5 x 0.5 threaded filter to an SM1 lens tube. The unpackaged weight of this adapter is 2.95 g.