How the Water-Saving Neoperl PCA Technology for Faucets Works 

Faucet or tap aerators are a key component, mounted at the tip of the spout to regulate and aerate the water flow.
With a faucet aerator, there are two options to control the water flow. The more common option is a fixed orifice designed to allow a predetermined flow at a specified pressure. The other option is to compensate for variations in pressure to achieve a constant flow rate. This is what Neoperl's PCA® technology does: PCA® aerators have a built-in flow regulator which produces - by means of its o-ring - a constant flow rate regardless of pressure fluctuations.
The Neoperl PCA technology is explained in this short video.