Silk is very absorbent, soaking up water in instruments better than any other natural material on the market, including both cotton and chamois. Most uniquely, silk is also very compressible, making it possible to pull through instruments with large variations in bore size. In addition, silk is lint free.
Bassoon swabs use a ball chain, which is very effective as a weight and more flexible than traditional straight weights.
The ball chain is non-abrasive and does not scratch the bore or other parts of the instrument when used properly.