After Britney Spears confirmed her engagement to longtime beau Jason Trawick last Friday, fans wanted to know everything about the ring, a four-carat diamond designed by Neil Lane.

Trawick — Brit's former agent — popped the question after working with famed jeweler Lane on the design, according to People.com. The site also reported that Trawick wanted a crown-like band. In addition to the mega-sparkler at the center of the tiara-style setting, the hubby-to-be also had 90 small round diamonds added around the band. Spears debuted the ring during a trip to Las Vegas over the weekend to celebrate her fiancé's birthday.

"Jason is a romantic and when I asked him to tell me about Britney and what the ring would represent to them so I could find inspiration, his response was always the same — she is his princess!" Lane told the website. "Jason didn't want an over-the-top ring with a giant stone."

Minya Oh, the author of "Bling Bling: Hip Hop's Crown Jewels," told MTV News she was pleasantly surprised by how understated the rock is. "The ring is so damn classy! It's [four] carats, which by Hollywood standards these days is practically microscopic," Oh said. "The setting is a tiny crown but both that and the thin diamond-studded band are done so delicately, from afar the focus is still on that bright white center stone. Nothing about the ring overwhelms her hand, and nothing screams, 'Please believe my relationship is real!' " She added, "This is the kind of ring a pop icon has when they're ready for something that means more than just the ring."

This is hardly Spears' first engagement ring, however. When her ex Kevin Federline popped the question back in 2004, the former back-up dancer gave the pop princess a five-carat diamond ring.

All this talk about rocks got us thinking about some other celebrity proposals, so we decided to spotlight a few memorable engagement rings.

Kim Kardashian & Kris Humphries
When it comes to size, Spears' ring from Trawick is small compared to Kim Kardashian's monster-size rock. When Kris Humphries popped the question earlier this year, he gave her a 20.5-carat Lorraine Schwartz diamond. Of course, the size of the ring didn't guarantee lasting marital bliss: the couple split after 72 days of marriage.

Beyoncé & Jay-Z
Like Humpdash, Jay-Z, who is expecting his first child with wife Beyoncé, also went the Lorraine Schwartz route. He gave his pop-star lady love an 18-carat ring back in 2007. The couple kept their wedding ceremony under wraps.

Kristin Cavallari & Jay Cutler
While it has been a bumpy engagement for former "Hills" star Kristin Cavallari and her football player fiancé Jay Cutler, the couple announced they were engaged again last month. Cutler opted to use the same 5.2-carat ring he'd given the MTV reality star back in April when he first decided to put a ring on it.

Hilary Duff & Mike Comrie
Before Mike Comrie asked mama-to-be Hilary Duff to be his blushing bride last year, he reportedly spent $1 million for the sparkler, said to be about 12 to 13 carats.

Katy Perry & Russell Brand
Russell Brand also gifted Katy Perry with a ring of about 12 to 13 carats when he proposed last year to MTV's 2011 Artist of the Year. The comedian asked the pop star to marry him while the two were in India. The couple would later re-create that magic when they also married in the country in October 2010.

Share your well-wishes for Britney and Jason in the comments!