It's Britney's super skinny waist, bitch!
In the sassy pic, the 31-year-old "Work Bitch" singer poses in a black leather onesie with cutouts over a spiked bra. She lifts her arms up in the air to show off sleeves made of black tassels. Brit also flashes an open-mouth smile while her long blond hair flows down her chest.
It sounds like all of Spears' hard work is doing a body good!