Spring loaded plastic Ball Cord Lock, best used with 1/4 inch or 3/16 inch bungee cord. Works with Para-Cord too. Use for seat strings, hatch cords, rudder tension lines, draw strings and stuff sacks. Hole is exactly 1/4 inch in diameter (some 1/4 in. cord may fit tightly). Diameter of body is about 3/4 inch.