Many safe companies are now using what is called a “composite” door design. “Composite” in this sense does not mean fiberglass or Kevlar but rather a composite design of a formed steel outer shell filled with sheetrock. Unfortunately, many companies use 12 Gauge or thinner steel (14 GA., 16 GA.) when manufacturing their composite doors. These are easily defeated with an axe or sledge hammer. Some merely spot weld the door shell with the end result being a door that may appear to be 4 inches thick but can be easily smashed open with a sledge hammer. Composite doors do tend to offer superior fire protection over plate doors mainly because the sheetrock encapsulated by the outer shell acts as an absorbing heat sink. When constructed properly, composite doors offer great fire protection and security. For residential security we recommend that any composite door be fabricated from a minimum of 10 Gauge Mild Steel.