[msumpter]

I believe the two boosters were previously flown and were of an older block/generation (block 3 and 4 if memory serves me) where they are focusing on block 5 as the final revision and all future Falcon rockets would be this same standard. https://en.wikipedia.org/wiki/Falcon_9#Block_5

[SubiculumCode]

So, from that reasoning it might be less that they couldn't fly those rockets again, but that maintaining multiple versions of the rockets might not be in their financial interest. Thanks for the input.

[zrail]

Whoa, so not only were the boosters landed, they were actually reused from previous launches! That's doubly awesome.

[SubiculumCode]

Yeah. I'd say even more than double awesome. The falcon heavy launch was super important for Space-X, PR and investment wise. Trusting two used rockets for THAT launch shows real confidence in the re-usability of their rocket tech. Bravo.