An Essential Sports Bra: ThirdLove Flex Seamless Racerback Sports Bra This ThirdLove Flex Seamless Racerback Sports Bra ($55) is a medium impact bra, so it'll be a great option for everything from yoga to boxing. Plus, the colorblocking is so cute! Image Source: thirdlove.com ThirdLove Flex Seamless Racerback Sports Bra $55 from thirdlove.com Buy Now