Crystal Harris is showing off her new ice just in time for the winter chill.

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. Hefner had popped the question to Harris over the holidays.

"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.