Micro, small, medium and large are kind of general term or description of chenille sizing. One brands small might be another companies medium. You are better off in my opinion to use specific size measurements in millimeters. Not always easy to get this info but it can be found. Here is my experiences. Micro / 1mm, small / 2mm, medium /4mm and large / 6mm. On 1/16 and 1/32oz jigs with #4 and #6 hooks I most often use 4mm and sometimes 6mm chenille. On small bluegill jigs with # 10 and # 12 hooks I usually use the 2mm size.