The key has a narrow rectangular opening for key chains. I would say, dont put a key ring or chain in it. My key broke as i used the original mercedes key ring. Somehow the desgin puts a lot of pressure on then entire assembly.Does anyone know how to put the flip key onto a keychain? Is it possible? We would like to have the car and house keys all on the same ring, but we don't see a spot on the key to attach a ring to 
Our remote is from a '93 300SE. It is a flip key remote, with a large star button which iss used for keyless entry . . .
If someone else is doing something different, i would love to know.