Filter heads
The choice in filter head is important, as this will affect which water filters can be used, and should be considered as part of the water filtration total solution. Firstly, working backwards, choosing your desired water filter taking into account local water quality, application needed (cold or hot water) and flow rate desired will better allow you to work out which filter head is required.
Once the water filter is chosen, a head to fit that filter is required. This is generally only purchased on initial setup, and most commonly a single filter head unit is chosen. Depending on where the water isolation tap is you may choose a filter head with builtin isolation valve. If a higher floret of water is required, then you may choose a twin head which will double the flow rate of the individual filter, or a triple head to triple the flow rate, etc. On bigger systems gauges on inlet and outlet can assist as a drop in outlet versus inlet pressure is a good indication your water filters are getting blocked and need replacing, and this is crucial for expensive equipment which may be damaged if water flow rate is reduced. Water test ports can also be convienent to test the water quality post filter.