Gotta question here which I didnt find much answer from Google:
What is the difference between a sprung vs springless clutch disc in terms of durability, bite, and harshness?
Pics here:
Clutch disc with spring in center hub:
http://www.prostreetonline.com/apps/act/street_big.jpg
Puck-type clutch disc without spring:
http://www.prostreetonline.com/apps/act/xtremedisc.jpg