Adding a modifier to a phrase with a comma

Question

Here is the sentence in question:

"...line of performance apparel is perfect for any race, 5k to 50k. "

Is that the proper way to modify race? What is this rule called?

Answer 1

I believe this is just a case of a prepositional phrase in which the preposition is implied, rather than stated outright:

...line of performance apparel is perfect for any race, [from] 5k to 50k.

It's not incredibly formal, but I doubt it would be flagged as an error in most contexts.