Christie's auction house will auction the 25-year-old former The Girls Next Door star and Playboy Playmate's 3.39-carat diamond ring off in New York City next month, TMZ reported Friday.
While prior reports claimed Hefner paid $90,000 for the sparkler, Christie's has reportedly only set an estimate of $20-30,000 on it.
According to TMZ sources, Harris "couldn't bear to look at the ring anymore because it brought back bad memories."
Harris -- who got engaged to Hefner over the holidays last December but called off her wedding in June just days before she was set to walk down the aisle -- reportedly attempted to return the engagement ring to Hefner shortly after the split, but the 85-year-old Playboy founder and editor-in-chief refused to take it back.
"It was the right thing to do," Harris, who had dated Hefner for two and a half years prior to their engagement and termed their breakup a mutual decision, told RadarOnline about her overture at the time.
The former Playmate reportedly stopped by the Playboy Mansion to give Charlie, a dog, and the ring back to Hefner. However, in addition to telling Harris to keep the ring, Hefner told his ex-fiancee to hold onto a Bentley car he had previously given her.