Sorry i do not have any info on the spring.
I was at school and walking by the electronics lab and there was a small box
full of them listed "free" so I snagged them. They are real silver coated, some sort of electrical contact. One end is larger than the other and the spring can be screwed togather. I sent out about 5 envelopes of 100 to guys and half of them got chewed up at the post office. Then I got the coast lock swivels from walmart and I was golden. They work great and are basically indestructible. I just put the hook on the keeper and reel them down and put them in my ice rod case without a hitch. Here is a compariso

n to a lighter spring. I also have springs from your bobbers down and they do sell similar ones. To attach it i slipped the spring in the tip rod guide but not in the eye and then wrapped it with nylon thread and then epoxy coated.