This is a replacement supercharger pulley for the TRD/Magnuson Supercharger for the 3UR-FE 5.7L V8 engine found in the 2007+ Tundra, and 2008+ Sequoia.
This pulley is 2.345″ where the stock one is 2.45″. The normal increase in boost approximately 2 PSI over the stock pulley depending on combination and ambient conditions.
Installation requires removing the stock pulley with a strong gear or supercharger pulley puller and a special tool to press it onto the input shaft. You can have this done at your local speed shop or you can purchase the URD Press Fit Installation Tool to do it yourself.