There are keys like these with the large plastic at their base that cannot fit. There are transmitters for electronic locks or alarms with a smaller hole that the screw of the keyring cannot pass through. Unfortunately, therefore, while it is very good for most keys, you end up adding 2-3 more items externally to the keyring, which negates the whole point of the keyring that in my opinion is (a) not to jingle (b) the keys not to damage other contents of pockets/bags, etc. In terms of build quality and as an idea, it is excellent, but in practice, it turns out that the whole system does not work as you expect.