What is the quick review?
What models and sizes are available?
How is it built?
As we mention above, the major difference between the 2017 517 Omaha and the 2018 518 Omaha is the use of a different end cap. the 2018 version uses an newer composite that allows for a better sweet spot towards the end cap and a little more durability.
Ultimately, however, the 517 was a really great single piece aluminum bat. And the idea that an end cap somehow changed the nature of the beast is silliness. The 518 is the very close relative of the 517 and we'd struggle to suggest, with a straight face, the bats are different.