Min, Fei, and Hyeri test out their flexibility against contestant with back of steel on 'Star King'

miss A's Min and Fei along with Girl's Day's Hyeri competed against a contestant known for her back of steel on 'Star King'!

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The Chinese contestant, In Ssu Ri (27), who claims the title as 'girl with a back of steel', amazed viewers with her flexibility to flip her back 180 degrees to perform stunts.

Fei shared, "In China, there are a lot of flexible people. There are a lot of people like her in dance schools. But the stunt in which she flipped her back and drank water, you really need a lot of back strength for that."

Hyeri then attempted to follow the contestant by lifting one leg up to her neck and perform archery at the same time with the help of fellow member Sojin but failed. Fei also tried to perform the difficult stunt of flipping her back and drinking a glass of juice while Min successfully performed a split while keeping a bottle from falling on her head.

Check out the amazing stunts below!