It has a moderate hardness that wont scratch the float, but does not pass through the entire part. This stopper is used by threading the yarn through the weaving thread to prevent the floats from falling down to the Harris side. Made of a material with moderate hardness that does not lose the knot even if the weight of the float. Of course, there is no damage to the thread. Adopts a stealth black color that is discreet in water and does not leave you alert. Tapered top line entry for easy threading. Threading is easy and smooth.