The Princess of Wales is wearing Princess Diana’s sapphire engagement ring, which has set trends for decades, along with her Welsh gold wedding band and three eternity bands. Max Mumby/Indigo // Getty Images Kate Middleton’s stack without her engagement ring. “Diana’s ring brought colored gemstones back into the engagement ring conversation,” Mazuera explains. Many brides stack their wedding band and engagement ring at least, and Kate’s are carefully designed to sit flush so they won’t damage each other. This is important for anyone designing a ring stack, Boc explains: “With something very precious like an heirloom engagement ring, it’s important to make sure that the stack won’t create damage or wear over time.