These o-rings are a high quality o-ring made from Nitrile N70 compound. These fit all ball lock and pin lock kegs. The dip tube o-ring is easy to replace and is simply a matter of removing the post first then lifting up the gas and liquid dip tubes to reveal the location of the o-ring.
These O-Rings are the correct replacement for the O-Rings under the posts on your Corny kegs. When the o-rings are new they have a round cross section however after being used for some time they turn into a square cross section so dont be alarmed if you take the old one out and wonder why the new one is round. It's simply that the old o-ring has changed shape over time.