NDK Hub Bearing Seal
This is the seal in the back of the bearing Hub that seals against the front of the Spindle.
NDK are a well renowned Japanese manufacturer, these Seals are made to Genuine specification, and are a great affordable alternative to Genuine Parts.
Most aftermarket seals on the market are a Chinese Copy and often they don't quite fit right, or the rubber material is to firm.
it is also common for these to be installed back to front, the twin lip seal should be on the outside once the seal is installed, so that it can seal against the Spindle.