One valve head suitable for Medela Swing & Harmony
Also can be used with Spectra breastpump, Autumnz Bliss & Passion breastpump
The yellow valve should be removed from the breastshield connector after each pump use.
The white membrane should be removed from the yellow valve and both parts cleaned. If these parts are not cleaned milk will likely be trapped between them leaving the white membrane sticky.
This will prevent the white membrane from moving properly during pumping and decrease effectiveness of the pump.