https://www.youtube.com/watch?v=b04yq4lmD0o
I found this to be pretty interesting. I always wondered why they looked different compared to residential light strings. I wonder if you can get commercial light strings anywhere?
Here is a video of a light string being made:
https://www.youtube.com/watch?v=jC3UBAxiQyY

I would think that you buy them from a commercial electrical store, or directly from the manufacturer.

I'll have to check out those vids..always wanted to see how xmas lights were made :cool:

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You can buy the commercial grade lights online.