Sizing of Zip & Link beds

I'm a bit confused. You list the sizing of zip and link beds as follows:
King size ziplink (5’0 x 6’6) – Comprising of 2 x 2’6″ x 6’6″ beds
Extra king ziplink (6’0 x 6’3) – Comprising of 2 x 3’0″ x 6’3″ beds
Super king ziplink (6’0 x 6’6) – Comprising of 2 x 3’0 x 6’6″ beds
but when I look at specific mattresses 'Extra king ziplink' is always listed last, which makes me think this must be the biggest i.e. 6'6 ft long?Which is correct please?