1-3/8" DOOR: Refers to the thickness of the door. 1-3/8" is the standard size for an interior door.

HOLLOW CORE: Refers to a door that is hollow on the inside. These doors are less exspensive and are not as effective at reducing noise from room to room. They also are much lighter to carry and are therefore easier to install.

SOLID CORE: Refers to a door that is solid throughout. Solid core doors are more exspensive and much heavier. They provide a sturdier feeling door that will also deaden noise better throughout the home.

1-3/4" DOOR: Refers to the thickness of the door. 1-3/4" is the standard size for an exterior door. These doors are thicker to help provide a sturdier door for security purposes and a higher insulation value. Some people will occasionally use this size for interior doors.