Steeda's aluminum driveshafts for the 05-08 Mustangs are the best aluminum 1-piece driveshaft available! These driveshafts do not use a flange which can contribute to vibration. Instead they come with a completely new pinion flange which the driveshaft directly bolts to. The GT model driveshafts are a tapered 3.5" to 4 inch design giving them extra clearance needed to avoid interference that can happen on lowered cars with full 4" shafts. Weighing 24lbs less than the factory GT model driveshaft this 1 piece driveshaft greatly reduces rotating mass giving you up to 2 tenths improvement in 1/4 mile performance!