Sold individually.
Choose the pole diameter from drop down menu.
Suitable for 19mm, 28mm and 35mm poles depending on selection. 
19mm bracket length - 9.5-10cm (Back plate - 5cm)
28mm bracket length - 10.5-11.5cm (Back plate - 5cm)
35mm bracket length - 12-14cm (Back plate - 6.5cm)