I think they are a TOTAL waste. Instead, buy a 10# Kettlebell and go to YouTube and find good work outs for women. Steve Cotter on YouTube is the expert on basic form, but there are other videos done by women that are good. One video by a guy has 25 basic exercises and that is good.
I have 2 10# Kettlebells so I can hold them one in each hand, or put the two and have 20# which works okay. I want to buy several more that are heavier as time goes on.