I know that many of you know this info, but for those that come to the forum to find out which O2 sensor to use, here is some info:
Most stores carry the Bosch, Denso and NGK brand, but Bosch recently changed the product number which resulted of a price difference of almost $100
For non CA engines, the O2 sensor behind the cat is the Bosch 16700. For the engines in CA, you need the Bosch 16698. The difference is the connector, so make sure to check you got the correct one before you install.
Bosch changed the product number from 16700 to 16002, so forget NAPA, Advanced Autoparts, etc as they have the note in their system that refers to the new sensor. If you need to buy the sensor behind the cat, just go online as I did and order the 16700 as they are still available, and save a lot of money.