* Change 2 Part Black {3684 Slope 75 2 x 2 x 3 - Undetermined Stud Type to 3684a Slope 75 2 x 2 x 3 - Hollow Studs} {Alternate to Regular}
* Change 2 Part Black 3684b Slope 75 2 x 2 x 3 - Smooth {Regular to Alternate}
Comments from Submitter:
Systematic change for new catalog part. Also, switching variant 'a' to be the regular version and 'b' the alternate in case 'b' ever gets phased out (which I hope it does).