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These are the radomes for the FASS radar system as used on the Hawker Siddeley Nimrod AEW.3, and proposed for many other aircraft.
The front dome has a sharp nose, the rear dome is more rounded and has an asymmetric profile (the top half bulges a bit more than the bottom).
I can't set the available materials separately per scale. I don't recommend ordering the part in 1/144 White Natural Versatile Plastic, it's difficult to clean up a part that small. For 1/72 WNVP is fine.
The model marked as 1:55 is a 1:72 dome scaled up by a factor of 1.33.
The model marked as 1:120 is a 30mm wide dome.