There is a good nylon or teflon washer on one end of the spring. The other end also needs a washer as it sticks every time I move the clamp. Yes, I have extra pucks, but they really had to think of everything. I have other grips with the same issue but as they are large this seems to be a bigger problem. The springs get stuck in the track. The nice thing is that these are really big clamps, but they also fit on smaller rails. The blue clamp measures almost 4 1/2 inches in diameter and is great for a variety of materials. In terms of height, they can handle materials up to 2 1/2 inches thick.