This is one of those "I should have done it long ago" stories. We have been using a faucet attached PUR filter with the plan to replace it sometime with a better water filtration system.  After 20+ years we bought a new fridge and decided finally to take action. I saw the Circle Reverse Osmosis System which appeared that it would neatly fit under the kitchen sink. The cost of replacement filters was about the same as the PUR albeit much much better. In addition to the supplied faucet we have it connected to the fridge. Crystal clear ice and AWESOME tasting water.