Since these doors are designed as an add-on, you can use them anywhere they'll fit, not just with the MFK2 series. These are a fairly recent pattern, presumably knocked up from corrugated zinc and steel bar as an economical replacement for a wooden original. The model's double sided, giving you the choice of a new or more weathered finish.
Their position in the screenshot, providing a replacement entrance for the blocked-up one on the Double-Door basic unit, is probably the most obvious, but they'll also fit on the Machine Shed Unit with a tiny bit of dropping.