question about brake pressure switch

[stevek]

I just purchased a new brake pressure switch from kirban and wondering about the o-ring that is installed on it, it is installed on switch just past the threads and the old one that i took out of my 86 gn the o-ring was located over the next ridge which is the last grove where an o-ring could go. Was wondering if there should be two o-rings on it or one, and which grove it goes on, seeing how the old one only had one on the last grove i was just hopeing if there was two on it the other one didnt break and fall down into master cylinder.any help would be appreciated thanks