Mullion Glass Door Cabinets. Mullions, dividers that create a lattice across a glass door cabinet, provide a particularly dressy touch to a kitchen design. Personalize your kitchen with your choice of art glass or other insert. CliqStudios glass door cabinets, available in select door styles can be ordered in wall cabinets 15â³, 18â³ and 30â³ wide and 30â³, 36â³ and 42â³ high.