Meghan Markle won't be wearing Kate Middleton's tiara when she walks down the aisle for a reason.

A number believe that Markle will wear a tiara on her wedding day. There are speculations that she might use the Strathmore Rose tiara of the Spencer tiara but definitely not the one that the Duchess of Cambridge wore on her royal wedding in 2011.

The Cartier Halo tiara that Middleton used when she walked down the aisle to exchange "I do's" with Prince Harry was from Queen Elizabeth II. However, it's not available on Markle's wedding as it is on display at the National Gallery of Australia from March 30 through July 22, People reported.

The headpiece will be one of the 300 tiaras, necklaces, brooches and earrings that will be featured at the jewelry show "Cartier: The Exhibition." The Queen received the tiara as a present from her mother on her 18th birthday.

Since the Cartier Halo tiara is not available, royal expert have different opinions as to what Markle would wear when she ties the knot with Prince Harry. Former royal butler Grant Harrold believes that will opt for the Spencer tiara to give a nod to Princess Diana.

"If she does decide to wear a tiara, I believe she may opt for the Spencer tiara which was famously worn by Lady Diana Spencer on her wedding to Prince Charles, and on many more occasions throughout her life," Grant Harrold, former royal butler, told Femail.

"This could be a way for Prince Harry to involve his mother in his big day, as Prince William did when he gave his future wife Kate Middleton his mother's engagement ring," Harrold added.

Meanwhile, On the other hand, Rebecca Share, a jewelry expert and gemologist, thinks that Markle will walk down the aisle with Queen Mother's Strathmore Rose tiara.

"Due to their unique styles, it is thought that she may wear the Strathmore Rose tiara or have something totally unique," she said.

It's also possible that Markle will wear a new tiara that is customized for her like what Sarah Ferguson did when she married Prince Andrew. An expert predicted that if the actress would do so, her headpiece will cost over $300,000.

"This picture-perfect classic is made entirely out of diamonds set in platinum with floral scrollwork and a large diamond of around 5 carats sitting on top," Grant Mobley, a gemologist and director at Pluczenick, told Express. "With the value of a top quality 5 carat stone like this tiara topper combined with the platinum and other diamonds, the value of this tiara would easily be more than $300,000 today."

What tiara do you think will Markle wore at the royal wedding? Share your thoughts in the comment section below.