Steerer for the rear headset. To use as a replacement if the original tube is cut and a higher bar position is wanted. 
 
Fits all GinkGo bikes
 
 
Material: Aluminium
 
Dimensions:
length 250 mm,
diameter:
tube 28.6mm (1 1/8"), bearing seat 30mm, bottom 35 mm
 
Weight - 130g