Discraft says this about the Tracker: Discraft Stability Rating: X-Line 1.6; Z-Line 1.8; ESP 1.8
The Tracker(tm) is an extra long range driver with pinpoint accuracy and superior performance. Displays flight characteristics similar to our popular Buzzz midrange, but longer.
This disc has been discontinued and is only available in Fundraiser plastics, if at all.
About X-Line Plastic
High durability, excellent grip, even when wet, more consistent flights.