Ok so I have been through hell and back on this one. It is the pin that holds the brake pads on. I went to the Nissan dealership and they ordered the wrong part. I gave them my vin to order the right part and the man said that he couldn't just order the pin, I would have to order the entire brake caliper (which is rediculous). I took the pin to Napa and they couldn't match it up with ANYTHING they had. I think now my only hope is to find one in a junk yard. :-( I miss my X.