David Livingston, Getty Images

Crystal Harris has some new ice to play with.

The 24-year-old May-September fiancée of Playboy mogul Hugh Hefner posted a picture of her impressive round-diamond engagement ring on Twitter today.

"For those of you asking to see it here it is....My engagement ring from my love @ Hugh Hefner," Harris tweeted.

She then posted a close-up of the whopper ring, which needs no enhancement. It appears to be a multicarat round, brilliant-cut diamond set in a platinum band with smaller-diamond accents.

Hefner surprised Harris, his No. 1 girlfriend for more than a year, when they exchanged gifts on Christmas Eve.

"I gave Crystal a ring. A truly memorable Christmas Eve," Hefner tweeted after the proposal, later clarifying that the bauble was indeed an engagement ring. "I didn't mean to make a mystery out of it."

Harris reportedly gave Hef a framed picture of their dog.

The couple has not announced a wedding date, but the impending marriage will be the third for the 84-year-old Hefner and a first for Harris, who is young enough to be his great-granddaughter.

In case anyone's wondering how Hefner's long-suffering former main squeeze Holly Madison feels about the engagement, the Playboy is likely to find out soon. He tweeted today she'll be filming an episode of her reality show, "Holly's World," at L.A.'s Playboy Mansion next week.

Meanwhile, this is just the latest ring flashed in a holiday season full of sparkles.

Read about actress Reese Witherspoon's rare 4-carat Ashoka cut engagement ring.

And of course, we're looking forward to getting a look at expectant actress Natalie Portman's engagement ring from ballet dancer-model Benjamin Millepied.