The radio aerial on the Abarth/Fiat 124 Spider (and the MX5) is rather long and replacing it with a shorter/stubby aerial is a common thing to do. However, the base of the aerial mount needs to be covered.
This surround is for the Richbrook aerial found at Halfords here in the UK and is shaped to friction fit snuggly to the aerial. As this is to be exposed to UV, weather etc, PLA is not suitable for this application (long term).
The author hasn't provided the model origin yet.