I wore these tights for the first time recently and the elastic in the waist gave way almost immediately, as if they were old and perished, making them very uncomfortable (and embarrassing!) to wear all day long. I am a size 12 so I thought small-medium would be ok. Obviously not! When I first put them on, they felt ok. You can see from the attached photo that the crotch suffered too from the constant hitching up that I had to do all day. So disappointing because I love the colour! I would welcome a substitute pair but I'm worried the same thing will happen.