Love these! I use them in my toddlers hair- although I definitely don't find them to be "invisible" they definitely last all day and don't slide around in her hair or pull it when I'm taking them out.
Only thing I do find is that they are quite stretchy so they stretch out of shape easily and can snap (which hurts if your fingers are in the way!)
Firstly love these as a product and I always have a packet in the house. I do normally purchase black or white (I got these ones as a rewards from this site).
Due to the lovely bright colours I would not label these as invisible.
Also if you are more of an ecofriendly person these are not the product for you. I find they can never be reused the next day, though they do last all day in your hair which is great