ProMaster Double Spigot 1/4-20m to 3/8m

The Short Double-Male Round Spigot with 1/4"-20 and 3/8" Threads from Impact has a 5/8" (16mm) diameter and is made of brass. It fits 5/8" receivers, and can be used as a replacement for the adapters that come included with many swivel umbrella adapters.