From Hack Fab:

This is a brass rear hub for the Losi Mini line (Mini-T 2.0, Mini-B, Mini Drag).

One thing oval racers like is left weight bias. Brass hubs are popular in 1/10 oval racing as they add unsprung weight on the left rear tire to help keep it planted in the corners. With the Losi Mini line, the hubs are so small, that just making them out of aluminum or brass would have little difference. We thought outside the box and tried to get as much material onto the hub as possible, giving it some sizable mass. We added "ears" to the hub to give it more material for added weight. We also made it a drop-hub to provide it some  added adjustability.

This will work with Mini-T 2.0 or Mini-B rear wheels. It DOES NOT work with the TLR Mini-B CVA's as those have a larger inner bearing. This hub has been tested with stock Losi dogbones and MIP CVD's. For the MIP axles, some shimming with 4mm (ID) shims might be advised.

The stock rear hub weighs approximately 1.23 grams (.043oz). The brass hub weighs almost 20x as much, at 23.57 grams (.83oz).

Sold as a single rear hub, as most will only want to run this on the left rear of their oval conversions.