Amazon.com : Neewer 2 Pieces Standard 1/4 to 3/8 inch Metal Male Convertor Threaded Screw Adapter Spigot Stud for Studio Light Stand, Hotshoe/Coldshoe Adapter, Ball Head, Wireless Flash Receiver, Trigger : Electronics
Spigot Adapter Spigot x Insert - AquaCave.com
NIBCO 4 in. ABS Soil Pipe Hub x Spigot Adapter C5805HD4 - The Home Depot
Spigot adapter 28 mm to 16 mm - short
Manfrotto 3/8" + 1/4" Adapter Spigot 147 B&H Photo Video
Manfrotto Spigot Adapter 16 to 17mm 185 B&H Photo Video