Keira Knightley and James Righton in London on May 27, 2012. Credit: XPOSUREPHOTOS.COM

Right on, James Righton!

When choosing an engagement ring for Keira Knightley, Righton selected a stunning yet classic style. The Klaxons rocker, 28, and the Oscar-nominated actress, 27, confirmed their engagement Friday, and since then Knightley has been flaunting her new bling.

"This is truly the most classic of all engagement ring styles," jewelry expert Michael O'Connor tells Us Weekly. "It's a solid platinum band with a brilliant cut solitaire diamond, approximately 2 carats. Estimated price tag is $40,000."

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O'Connor adds, "Not only is this ring sophisticated and timeless, but I love that she's wearing a platinum setting that you can find within most budgets."

On Sunday, the newly engaged couple packed on the PDA while going for a stroll in London -- with Knightley's diamond on full display.

The couple have been dating for about a year before Righton popped the question. It will be the first marriage for both.