These spirex slide-only sash balances come in four tip colours, each colour denotes the sash weight it is used for, please use the chart for reference of correct tip colour for sash weight. The measurement indicates the length of the silver tube. For balances of 53" long or more, please contact us directly. 
 
If you are replacing broken balances, please contact us so that we can help you choose the correct weight. Sometimes incorrect balances are fitted when the sash weight is not known or is incorrectly calculated, we can help you to avoid this.
 
For each window you will need a top and bottom pair, one for the top sash and one for the bottom sash.