*Note:* A tip to new buyers: if you have trouble fitting it to your cooling system, as I did on a 2006 Kia Spectra5, look very closely as how the adapter is fitting in the opening of the radiator or fill-up point. The radiator I was dealing with has a small lip just beneatht the opening that means a round insert won't go far enough in to secure with the collar. I took a fairly sharp knife and made small conservative shaves on one side of the adapter end, giving it a flat spot. After a few trims it fit snugly and was able to burp the system beautifully. Still works on other vehicles and saved me massive hassles on the Kia.