Black disc cap 24/415 neck.

For your interest:
All caps have two measurements to show what bottle they will fit.
Here, 24 refers to the diameter of the neck of the bottle; 415 refers to the length of the neck.

If a 24-neck bottle has a short neck, it will need a 24/410 cap.
If it has a long neck, either a 410 or 415 cap will fit, but the 410 won't come right down to the shoulder. It can look a little awkward.

A 415 neck won't fit a 410 bottle.