Apparently it's a deep well socket with a slit in the side of it to go around the wire. I got a call from snap on the other day saying the special wrench it takes to undo the O2 sensor is $90.00 I found out about the O2 sensor socket from an engineer here at my work. He said it works on most cars but didn't know about BMW. Does anyone know if this will work to change the O2 sensor so I don't have to go to a shop or buy the $90.00 wrench?? Thanks guys!!!