Mira Excel/Select thermostatic shower cartridge valve assembly - part number 903.33 (1.903.33.6.0) with a purple hub. This spare part is suitable for high and low pressure installations and is designed for Mira Excel showers made prior to 2003. It replaces older models, 903.27 (Low Pressure, yellow hub) and 903.28 (High Pressure, green hub), which are now discontinued.