Composite Observations Model pattern + rails?

Question

Ruby on Rails

Description of the pattern: here (picture 4, 5 and next to the text. this is the main one)
In general, Moscow understood the pattern, but there is a problem in the implementation on the rails. It is not clear whether it is worth using STI (more precisely, I am 80 percent sure that it is necessary, but something like that :)). Yes, and in general I'm stupid with models. Specifically, the implementation of the pattern in the form of Product - Specification is of interest.
PS Why so, and not differently? Because here the interest is purely academic :)
PSS We talked about STI. meant Polymorphic Associations