The gauge and length of a string is very important to ensure a good tonal quality and stable tuning. One should consult the following table as a guide to string thickness and tuning. A string that is too thick for its given note will either break under the extreme tension, or it will quickly wear away the surface of the bridge causing an undesirable sound. When the contrary applies and the string is too thin, it will tend to be unstable in its tuning and note reproduction and will emit a thin, twangy sound. The four strings on a tanpura are tuned in three frequencies, the middle two being the same. The following table will give you an idea into the types of strings and their different gauges for their tuning possibilities. Of course every instrument has its own requirements, and likewise, every musician his or her personal preferences, so a certain amount of flexibility is necessary. If your instrument requires a higher pitch then a lighter gauge is recommended. Likewise, a lower pitch will require a heavier gauge. The average lengths, gauges and tunings are stated. However, it must be stated that there are many views and ideas on the particular gauges to be used, but these are my preferred gauges.