You should find a little information about string gauges is useful when selecting a string.
A thinner gauge should provide improved response and a thicker gauge extra durability.
Many strings are available two or three different gauges.
The measurement is the diameter of the string measured in millimetres. The most common values are 120, 125, or 130 which is the actual measurement multiplied by 100.
Use a 125 gauge for response and up to 135 and sometimes 140 for durability. The most popular gauge is 130 which provides the best balance between performance and durability
These are more durable and a thinner gauge can be used. The most popular are 120 or 125, but some players use a 130 gauge.
Sometimes a string will be described as a 16 or 17 gauge. This is an alternative method used by some people. Both measurements are usually shown on the packaging.