These are a ramp and slide style diff. Very good, and can be set up in many different ways, For street use, a 1.5 way is the best way to go. The 1.5 way is a common diff for racing as it does not give understeer on de acceleration through cornering but gives a hard clamping force under acceleration. These diffs can usually be set up as preloaded or non preloaded depending on what application you want. Porche Cup use a 1.5 way asw well as Lamborghini Gallardo as standard for their GT3 and road cars. (earlier Gallardo use a 2 way)

Did you get them from the USA? Or local?

For some info there is a video, it doesn't explain much but it gives you a general idea. KAAZ Video