I don't get it...why?

[Harryburgundy]

http://cgi.ebay.co.uk/PowerCranks-Adjus ... dZViewItem
Erm....am I missing something :?:

 

[P20]

They're a roadie training tool. Which bit didn't you get?

 

[Harryburgundy]

The adjustable length bit.

 

[psyclone1976]

They are used by physio's etc on indoor trainers to help with rehabilitation of athletes or by trainers to measure performance etc, wherever a shared bike is used amongst lots of different people with different legs lengths etc....(I think!) :?