Fire Tank Pirates

The Firetank Pirates are an infamous and notable rookie pirate crew discovered on the Sabaody Archipelago around the time the Straw Hat Pirates arrived there.

Crewmates
They appear to be based on a mafia family, and many of them are dressed in suits, with coats strapped to their shoulders, and/or wearing fedora hats. Hence they, (or at least the captain) like Crocodile, have a very Italian Mafia aura.

Crew Strength
All of them appear to be consistently armed with rifles, save for their captain, who has an army of men inside of him, who work his body like a fortress, thus giving him military advantages. It is shown that many ride horses into battle. .

You guys have already lost... in sheer military force.

It can be presumed that they are very strong for them to have made it all the way to the Sabaody Archipelago and for their captain to have such a high bounty. They, like the Bonney Pirates, were completely unharmed by Kizaru's raid. Their current fate is unknown since they were pulled toward a mysterious, gigantic black sphere in the New World.

Ship
Their ship seems to have a fortress theme, as seen in chapter 581.