This is a chrome-plated Avenger/Manfrotto C590 Conka Bonka Stand Extension Kit . This three piece kit can be used to extend the height or reach of a cine-stand or boom.
Each extension is fitted with a junior stud on one end, and a locking junior receptor on the other. Their respective lengths are: 26.6"/67.5cm, 10.6"/27cm, 6.0"/15cm.