I don't know what swivels they use. It reminded me a bit my connection when I saw photo of nunchaku from Silver Fire, but there was a stopper so I couldn't see everything. I use swivels like these on the photo from my earlier post and I don't have any problems with them, they can be used as a substitute. Homemade chucks won't be original chinese nunchakus, but homemade are cheaper and can be similar to original.