GENUINE JDM NISSAN O2 SENSOR | SR20DET | 12mm SKINNY TYPE
 
Brand new OEM SR20DET O2 Sensor for S13 . These are OEM Nissan NTK O2 sensor. Changing out your old sensor to a new one usually would improve gas mileage. For S13 models, there's 2 type of O2 sensors. There is the Large (FAT) (blacktop) and Small (Skinny) (Redtop) type, both have 3 wires. Images shown above are for the skinny Redtop type.  Either model will work on the engines, the only difference is the thread size.  
 
Part #22690-50F00