Our system is built on 3/8". So you will need a 1/2" female adapter to 3/8" male adapter.
(Here's an option on Amazon)
You might want to have a plumber stop by just for this part of the installation or get some plumbing tape for the metal to metal connection. Our part has a silicon seal so it won't leak but when you put the adapter on your existing plumbing, metal to metal can have issues. We don't sell these but we have this come up every once in awhile. Most homes now are 3/8".
Feel free to reach out if you have any issues!