This adapter is a made by solid aluminum rod with a stainless steel threaded shaft which loosen in Dia. 25mm and extension to Dia. 26mm by tighten the knurled collar. It allows securely locking into a dolly's 1" seat post or pushing bar receiver. On the other end it comes with an inside diameter 1-1/8" junior receiver that can accept any equipment with junior pin like extension pole or umbrella. The junior receiver with O.D.48mm for standard 1-1/2”(48.3mm) speed rail clamp to access as an starter to build up rail system on dolly as well.