This doorbell is an easy install.  Drill a small hole through the wall.  Place the outside part of the doorbell there and then place the main part of the doorbell inside and install with two screws .  It is ready to go.  The inside has an old fashioned look.  The bell makes a pleasant sound.  I have not cleaned the brass.  Some people want it to look weathered and some don't.  The part that goes inside measures about 4.5 inches in diameter.