Mustang:  Both sets are on $0.05 metal rings that I used to replace the too-small ring that is normally on the remote transmitter.
951:  Set 1 (includes ignition, alarm and wheel keys) is on a little leather "Porsche" key fob that the previous owner gave me.  Set 2 (only ignition and alarm key) is on a free "Duracool" keychain that I got when I ordered refrigerants.
914:  Set 1 is on a $0.05 metal ring.  Set 2 is on a free keychain that I got from my mechanic.
ZV