Got this from Malaysia years ago.
It is a clutch pack style rear diff. This allows for tunable lockup, and can help your DSM rotate around corners a bit better.
Realistically I'll never use it.
I took it apart to inspect it for noticeable damage.
The countersunk screws for the housing seem to have gone missing, but can be ordered or reused from a DSM diff. ( if this is an absolute deal breaker, I will remove them from my diff)
Comes with specific inner cups that will work for 1g 4bolt axles, and I believe 2g's.

Price included Paypal and shipping within North America