The Slack Cam Ring is one of the key components in the Profile Z Coaster® hub. It determines the amount of “Slack”or “Free Pedal” needed to engage/disengage the freecoaster mechanism. Slack Options: 20/33/45 Degrees (45 degrees = 1/8 of a crank), 60 Degrees (1/6 of a crank), 75 Degrees (1/5 of a crank), 90 Degrees (1/4 of a crank), 115 Degrees (1/3 of a crank). RHD or LHD available - Be sure to order correct drive side