"Don't expect anything too massive or obnoxious," a source tells RadarOnline. "This ring will be classy and under 4 carats."
People says Trawick got the bauble at jeweler-to-the-stars Neil Lane.
Of course, Britney will probably just be thrilled to have a sparkler she didn't pick out and (presumably) pay for, as was the case with the sizeable engagement ring she wore with former hubby (and dad of Sean and Jayden) Kevin Federline, whom she split from in 2006 after two years of marriage.
One thing that will be the same this time around: Britney will once again have a prenup, says TMZ.
Still, Trawick is reaping the rewards of Spears' love: She reportedly just splashed out $45,000 on a luxury, limited-edition motorcycle for his birthday.
So, as we send our congratulations to the happy couple, let's take a look back at their romance ...