You may notice that a lot of picks may simply be marked with a "M" or another letter
. Many people wonder what exactly these letters stand for. These letters are printed onto a pick to explain the thickness of the pick. Picks vary in thickness to accommodate different styles of playing. You may also see a small number on a guitar pick. This also is a measurement of thickness, and is almost always printed in millimeters.
T - A letter "T" on a guitar pick stands for "Thin Gauge". A thin pick generally is considered a pick between .50mm and .60mm. Thin picks have more flex in them, and offer a wide range of sounds that emanate from the guitar.
M - A letter "M" on a guitar pick stand for "Medium Gauge". A medium pick is generally considered a pick between .70mm and .85mm. Medium picks are great for beginning guitarists and offer a good balance between control and flex.
H - A letter "H" on a guitar pick stands for "Heavy Gauge". A heavy pick is generally considered a pick between .94mm and 1.20mm. Heavy picks are great for heavy metal players, as they allow for great attack on the strings, and wear down less during their strenuous play.
XH - The letters "XH" on a guitar picks stands for Extra Heavy Gauge" A extra heavy pick is generally considered a pick 1.21mm and above. A lot of bassists if they are using a pick will use this gauge.
When you see a measurement in millimeters on a guitar pick, that is telling you the exact measurement. Many companies offer in-between sizes to help give guitarist more options in their guitar pick selections. For instance a .63mm would be a medium thin guitar pick, and a .38mm would be an extra thin. Many guitarists often find a thickness they like and get very used to it. Professional guitarists can often tell if a pick is thinner or thicker even if it is only a fraction of a millimeter off.