Shower trap terminology help please

Looking for a new trap for a shower tray with a 50mm diameter waste and 90mm clearance underneath, and am a little confused…
For example: - I assume that "water seal" is the distance from the top of the waste to where a seal is created. In that correct? - What does the 90mm stand for? The diameter of the tray's waste? The technical drawings at the bottom of the page has no reference to 90mm - Would it fit into a 50mm waste hole? Again, no reference in the drawing.
Or this one:
Would it fit into a 50mm waste hole? I did notice that some traps are for 50mm and some are for 52mm holes (2" I assume).
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