If you want the under sink set up, go for the adapter found on the ebay page that says "1/2" tee & 1/4" ball valve, works for under sink water adapter
I believe it is the default adapter sent with the unit.I just turned off my cold water supply line and took it apart where the tubing from the faucet meets the pipe coming up from the floor. Since I have non-standard plumbing I just got a few cheap adapters from lowes and hooked the faucet line into the top of the unit's adapter, then hooked the bottom of the adapter into the cold water line coming up from the floor.
Now the unit just sits underneath the sink and when I need to make some RO
water I just drag my water bin over near the sink and turn on the ball valve.
Very easy, but can be troubling to set up initially if your plumbing doesn't fit the supplied adapter.
It should be noted that I am in no way a plumber.
I just took the adapter to lowes and told the guy what I needed, lol.