Step:
1,Look at the red ball closest to the eye until you see the phenomenon as shown.
2,Look at the yellow ball in the middle of the eye until you see the phenomenon as shown.
3,Look at the green ball farthest from the eye until you see the phenomenon as shown.

Description:
Brock String - used in fixing convergence insufficiency and sports training.
The basic purpose of the Brock String is to develop good binocular functions;  in other words to get both eyes working together well.  This activity teaches convergence - the ability to point both eyes more accurately at a target.
Size:beads diameter:1.8cm(0.7'')
       Rope length:260cm(102'')

Package includes:
1PcsX Cord
3PcsX Beads
1PcsX Case

Note:
1.Please allow 1-3mm error due to manual measurement.
2.The color may be different with the true item due to the screen display, pls understand.