Airgap faucets are sometimes needed for plumbing codes compliance. The installation is quite more complex than standard r.o. faucets, please study the faucet picture below before you make the buying decision. The diameter for the drilled hole needs to be about 1 inch to accommodate the 3 input lines.

Air-Gap Faucet Chrome $39

Air-Gap Faucet Stainless steel $65

APEC Reverse Osmosis Water Filter Systems