Plastic drawstring stop end, with metal spring.  height is approximately 2.7cm, with one hole of approximately 5mm diameter.  

To use: Press the button down, thread ends of cord through a hole, let the button go to hold in place.  Press the button to release the cord. Knot the ends of the cords together if using 1, or use 2 and knot each one separately.

sold singly.