Are o2 sensors different?

I need to replace the front o2 sensor on my 97 2.7 4x4 5speed. Is it a different sensor from the back? Anybody got a part number or place to get a deal?

 

I just want to know if there is any difference between upstream and down stream sensors. Thanks for the info, ima check rock auto. Thanks for the quick response.

 

I know one of the sensors goes into the cab and the other doesnt.. based on that alone id say the difference is the lengths of the wires.

 

This link may help http://www.tacomaworld.com/forum/1st-gen-tacomas/136703-o2-sensor.html

 

Sensors are all different.

It'll depend if;

Cali emissions or not
Manual transmission or auto
4x4 or 4x2

 

i ordered two from rock auto. It looked as if they were the same from 95-200 for both front and rear.