A weight stack isolator comprises an impact damper having a rail void therein configured to receive a guide rail of a selectorized machine. The impact damper is shaped to at least partially surround a section of the guide rail when received in the rail void, to secure the weight stack isolator to the selectorized machine. The weight stack isolator may include a slit extending from its outer perimeter to the rail void or the rail void may extend to the outer perimeter, to removably receive the guide rail in the rail void. The weight stack isolator can be positioned under a weight stack of the selectorized machine to absorb or dampen noise and vibration.