I'm a huge sticker mule fan. This is the 1st time I have ever been slightly disappointed. 
The charms are cute!! BUT!! The hole is not large enough to put on the average keyring thru the hole. 
I did find a tiny ring that would fit thru the hole. But... now I have to find 99 more to add to it. I was hoping clients could just add to their existing keyrings. But... nope. 
I would have given my usual 5 stars if not for that. 

So... make the hole bigger OR send rings with the charms that fit it. 

1st disappointment.