The Gardner ATTa 6-Magnet Alarm Roller Wheel is an optional roller for anglers using ATTa heads, letting you change both the colour of the roller and the sensitivity of your buzzer. It is available in a wide range of colours that match all the LED colours available, and more. Different roller wheels offer different sensitivity. As a guide, this means that: - With the 2 Magnet Wheel the Receiver beeps every 1 cm of line movement. - With the 4 Magnet Wheel the Receiver beeps every 0.5cm of line movement. - With the 6 Magnet wheel the receiver beeps every 0.33cm of line movement. Changing the Magnet Wheels couldn't be easier. Simply unscrew the retaining roller wheel spindle, swap the roller wheel, and replace the pin securing it in place by screwing it on using the integral thread.