Well heres some info from someone who actually has one, though you could just use the fucking search function to find this.

Its a standard open diff welded up, like the pics below.



Basically your rear wheels will turn at the same speed ALL the time.

Gives better traction in a straight line, and massivley better control when drifting/powersliding the car.

Makes your car look broke when doing tight slow speed manouvers etc

Makes your car more likely to understeer when you have full traction and/or not on the gas, esp if its an understeery POS like most standard RWD cars are unless you give it loads of gas.

You need to have your witts about you 24/7, esp in the wet, as once the wheels do spin a bit, its not the safe 1 wheel spinning that was engineering into the car as standard, the stuff you probably dont notice in most your driving, its proper 2wheels spinning oversteer fun.

I love it