OEM Nissan NTK O2 sensor, great replacement for the worn out ones that often comes with the used SR20DET motors. Change it to improve your gas mileage. For S13 models, there's 2 type of O2 sensor. FAT (Blacktop) and SKINNY (Redtop) type, both of which are 3 wire O2 sensor. To be safe, please look at your O2 sensor to determine which type you have and order accordingly.