The spring sash window is the modern day alternative to the traditional sash box window. This utilizes a spring mechanism which doesn’t rely the traditional weight and pulley system. 

Spring Sash Windows have come about as an alternative to traditional pulley weighted system, the change has come about from the high mentenance costs if pulley were to snap and needed to be replaced.

Overall both the weight and pulley systems you cannot go wrong both choices provide a timeless style of Traditional Box Windows. 

Sping sash mechanism is incased in a uPVC tube, which comes in several colors to match or complement the sash box windows allowing the implementation in most styles and environments.