bra bra A bra wasn't the only thing Miley Cyrus was showing off yesterday in X17's exclusive pix -- we also spotted a sparkly ring on her ring finger!

Could Miley be engaged at 17 to her boyfriend of only 6 months already?

We're thinking this ring says "promise" a little more than it says "engagement", but it's definitely not the purity ring Miley's sported in the past. Because, c'mon, we're a little past that now anyway, aren't we?