My daughter had real trouble latching from birth - if it hadn't been for these shields, I doubt we would have ever managed to successfully conquer breastfeeding. As it is, my little one is now 5 and a half months old and breastfeeding beautifully.
They are made of soft silicone, are easy to use, feel comfortable, are easy to clean and the sterilisable boxes are great for transporting them - the only issue I had with them is that after a little while the little slits that allow the milk to come through can crack and split; once this happens, you really have to throw them away and get new ones. It took me a while to wean her from these shields, but with some perseverance, we succeeded; if you are having trouble getting your baby to latch on and are considering bottle feeding as a last resort, but would still dearly love to breastfeed, ignore the naysayers and the disdainful sniffers - give these a go, they helped me immensely!