Girl group Fifth Harmony have been celebrating the release of their debut album, 'Reflection', all week, but the beauties now have another reason to be happy. 

Their latest single 'Sledgehammer', which was co-written by Meghan Trainor, has now been certified Gold by the RIAA. To be certified Gold by the Recording Industry Association of America, the track has to have sold 500,000 units.

Writing on their band's Twitter page about the impressive achievement, the stars explained that they're overwhelmed and so excited: "Holy smokes Sledgehammer went gold?!! You guys are THE BEST. Thank you so much."

Their catchy single 'BO$$' and early offering 'Miss Movin' On' have also been certified Gold by the RIAA. 

Member Camila Cabello shared a message with 5H fans this morning about the success of 'Reflection' and she told them that it's amazing to receive so much support: "I am physically exhausted/lost my voice/running on no sleep - but my heart is full. Thank you to everyone who came today, I feel so happy. There's no better feeling than when the pieces of the puzzle start to fit and everything starts to make sense."

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Watch a recent interview with the girls here: