Over the years I've bought a lot of music either in physical form or digital downloads. I've never really noticed any quality differences among mp3s I've bought from various sources until recently when I started buying better quality source and IEMs. I literally could care less about the bit...

I just purchased some Dunu Titan 1 iem's and the package included s,m , and l ear tips.  I've found medium fits me best, but now which medium is best?  Some have larger diameters than others and then some are red/black in color.  I'm not sure what the differences are or if the diameter size...