Taken from raceface.com
Turbine LP Crank
This is a cross-country specific crank. Use for any other type of riding is considered abusive. On pre-2001 versions (no threaded bosses on back of spider), if using without the inner ring you should protect the spider by threading outer chainring bolts into the threads in the crank.
Also in raceface.com
It is clearly mentioned that this is an XC/FR crank! So what is exactly the case?
And another big controversy....
The 4-Bolt Prodigy chainrings are manufactured from 7075 aluminum by precision forging and CNC machining. This is in sharp contrast to our competitors who manufacture via conventional stamping methods using cheaper 6061 aluminum alloys.
The crankarms are constructed with 6061 (cheaper ) alluminum.
Anyhow...that was fun enough.