Flush doors are simple door designs that have plain facings on both sides.  They can be interior (more commonly) but also exterior.  They are often used where space is at a premium,  and would probably be placed towards the “functional” end of the door design spectrum rather than the “style” end but as with anything, a little imagination goes a long way!  They may be kept deliberately simple in appearance to highlight other features nearby.

Flush doors may have a solid, hollow or stave core.  If the core is solid – low-density particle board or foam often being used to fill the space within the door completely – it may be supplemented with a type of laminate or plywood on each side.  Good for exterior doors as they provide more insulation and strength.

Note: Customized size door are also made as per your requirement.