Sweaty Betty Interval Seamless Navy Workout Mini Dress Sz medium in Navy Blue Excellent preowned condition. Looking for the perfect workout dress? Look no further than this Sweaty Betty Interval Seamless Navy Workout Mini Dress! This dress is made of a comfortable and durable polyamide and elastane blend and features a round neckline and sleeveless design for ease of movement during any activity. The dress comes in a flattering navy and white color scheme, and is designed to fit women's regular size medium.