An adjustable-size mop head assembly that may be used with a handle and a disposable cleaning substrate is disclosed. The mop head assembly includes a central frame section with a central portion and a lower substrate support surface configured to hold a disposable cleaning substrate. The mop head assembly also includes at least one adjunct frame section configured to be operably coupled to the central frame section and configured to move between a stored configuration, where the adjunct frame section is stored by the central frame section, and an extended configuration where the adjunct frame section extends from the central frame section to add width to the central frame section and the lower substrate support surfaces. A continuous web of disposable cleaning substrate that may be used with the adjustable-size mop head assembly is also disclosed. The continuous web of disposable cleaning substrate includes lines of weakness at regular intervals configured such that various widths of cleaning substrate are removable via the lines of weakness.