I own 6 of these shapers and wear them almost every day to work under skirts and dresses.  They really smooth you out under knits.  I like them much better than Spanx and they are made of iron - just wash and hang to dry and they last forever.  Also very comfortable to wear all day.  I highly recommend.  They are not super tight, so if you are looking for something to really suck you in, they will not do that.  I am a size 8, but need something to hold in my tummy a little bit and smooth everything out - they work great for that and are very comfortable.