When discussing squash string gauge, we are referring to the thickness of the squash string, measured in millimetres. A thinner string will feel better to play with, as well as being softer on your arm. A thicker string will not feel quite as good but will be more durable than a thinner string.
It is important to find a string gauge which suits your game, as well as being cost effective so that you are not restringing your squash racket after a few hours of play.
Squash string gauges are typically range from 1.10mm in thickness to 1.30mm in thickness, with around 1.20mm being the most popular squash string gauge.