Plastic drawstring stop end, with metal spring.  Width is approximately 2.7cm, with two holes of approximately 5mm diameter.  

To use: Press the button down, thread each end of your cord through a hole, then let the button go to hold them in place.  Simply press the button to release the cord.  You can knot the ends of the cords together, or knot each one separately if you choose to.

sold singly.