The CMT beading bit uses a smaller bearing than a round over bit to produce an extra inset bead along the lower edge of the cut, to create a detail otherwise not achieved with a standard round over bit.
To convert your round over bit to a beading bit, or vice versa, simply change the bearing.
Note: Be sure to keep the black bearing washer right side up to correspond with the bearing rotation when re-assembly can cause the screw to come loose.