The OG distance skateboarding wheels from Seismic. Back then these wheels were considered Large!
 
With 85mm the Seismic Speedvents are great in between Megawatts and Alphas wheels. With their narrow contact patch they push effeciently. Many skaters still prefer these wheels till today.
 
Why Split Duro?
In the front, we use faster, harder wheels, and in the rear, grippier, softer wheels. When pumping, the rear wheels need to have more grip. This is done by using a softer wheel for the rear. Also, with a classic +-0 degree rear setup, a softer, more flexy rear minimizes wheel lift. For the front, we use a harder wheel for fast side-to-side turns and better roll efficiency.
 
Specs:
85 mm diameter
49mm contact patch
Defcon Mint 80a (front wheels)
Defcon Mango 78a (rear wheels)