What to buy? (prob 3/4 to 1/4?). filtered water to refrigerator... Plumbing

Hi /r/Plumbing

This is what I'd like to get done:

http://ift.tt/1ny7sC1

Could anyone tell me what to buy in order for me to change the flow of the water please?

I have RO water filtering system and currently refrigerator water supply is directly from the main water line...

Submitted March 10, 2016 at 09:50AM by fruitdeeler http://ift.tt/1LdLvn8 Plumbing