This is the bearing that fits inside the Power Steering Tensioner. The Tensioner costs close to £80 and really consists of nothing more than this quality shielded bearing.
Two types exist, please see the Wiki page for the diagrams http://www.bigjimny.com/mediawiki/index.php/Drive_Belts
The type here is usually fitted to G13B engines. The bearing has a small centre so all you tend to see is the mounting bolt through the middle.
Simply press/tap the old one out using some old sockets and a vice and push the new one in.
NOTE: THIS IS NOT THE COMPLETE TENSIONER - JUST THE INTERNAL BEARING
The picture below shows a complete small hole tensioner
