The top overhang is a problem with this.  The best top ended up being a point.  The slit tends to separate during printing.  It might be slightly too short for the car key.  The only way to get the car key out is to take the plastic out 1st.  Thickness of the key case is still unknown.  It's thick enough to store all the keys, but it's manely empty most of the time so the keys bounce around.