Former heavyweight champion Frank Mir probably knows his division better than almost any other fighter that's ever been on the UFC roster.

He debuted in the promotion back in 2001 when the UFC barely ran six shows a year and the roster was seemingly as thin as the total number of participants during a season of 'The Ultimate Fighter'.

Mir helped lead the charge during his championship run in the UFC in 2004 to combat against the idea that all of the superior heavyweights were fighting in PRIDE Fighting Championships at the time.

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More than a decade later, Mir is still ranked in the heavyweight top 10 as he prepares for a showdown with Andrei Arlovski at UFC 191, so he has a unique perspective on the division that few athletes could ever have from the outside looking in.

He's seen the heavyweight division at it's best -- and for many years at it's worst.

Mir has watched as top competitors floundered in other promotions or came to the UFC and were ultimately exposed when facing other top level fighters.

As it stands now, Mir believes the fighters competing at heavyweight in 2015 are the best crop of athletes the sport has ever seen.

"I think this era right now is the best it's ever been," Mir told FOX Sports on Thursday.

The heavyweight division has always boasted big names. Whether it was Russian legend Fedor Emelianenko going on one of the most incredible runs in MMA history or the rivalry between Cain Velasquez and Junior Dos Santos in the UFC, there has never been a shortage of great champions and top ranked contenders.

The problem with the heavyweight division has always been depth.

With the heavyweight division's weight limit running anywhere from 206 pounds up to 265 pounds, smaller fighters have always been willing to cut down to light heavyweight rather than go toe-to-toe with someone actually shedding pounds before stepping on the scale.

The division has also historically thinned the herd thanks to heavyweights packing the biggest punch of anyone in the sport so longevity has been a problem for a lot of athletes when trying to stick around for more than a few years.

But Mir says all of that has changed recently as the UFC has become the top promotion in the world and the best heavyweights have flocked to fight there.

"I think in the past we always had top level guys but I think it dwindled off after four or five," Mir explained. "Right now there's guys that are 12th, 13th, 14th, that are great fighters in the heavyweight division."

As recently as five years ago, creating a top 10 ranking for the UFC heavyweight division alone was nearly an impossibility. Finding 10 worthy names was a struggle to fill a UFC specific rankings system, but now there are actually so many heavyweights clamoring to find a spot that ranking a top 15 is actually possible.

Thanks to the parity that now exists at heavyweight versus several years ago, Mir says this is definitely the deepest talent pool the weight class has enjoyed. From the champion all the way down to the No. 15 fighter in the world, there are no easy outs at heavyweight and Mir believes that's what truly defines this era as the best its ever been.

"I think the top 10 right now is extremely stacked," Mir said. "And I think it's the most stacked it's ever been."