I don't know exactly but what I have done with success in the past is just put Avery circular color paper stickers / labels on the end of the sensor - I believe I put them 2 or 3 thick (on top of one another) to be safe
My son replaced one of those sensors and got it shoved in too tight. When he went to start it you could hear it hitting. We removed it and of course the spacer was gone. So I just put it back in all the way. Tighten it enought that you could still move it. Then pulled it back about 1/32 of an inch. Started the car and it idled crappy. started to slowly pull it out or push it in until we hit the sweet spot where idle was best. Tighten it down and its been fine ever since. That was over a year ago.