ok here are the measurements i have been given that are more accurate
overall length eye to eye at full extension is 415 mm (16.38inch)
length eye to eye fully collapsed (no bumper or metal to metal) is 280 mm (11.02 inch)
Length of exposed chrome shaft at full extension is 133 mm (not including shaft in lower eye) This is then the actual shaft travel without bumper installed.
Length of chrome shaft in "cup" of lower eye is 13 mm
So the overall length or length of visible shaft is 133 + 13 or 146 mm.