I hate hard side travel bottles. You can never quite get all of the product out of them. That's why I was so happy to find these soft side travel bottles that have so many wonderful features. I traveled for 16 days in Europe and never needed all the product I put in these 3 oz. bottles, but was able to easily squeeze out the last of the product and clean the bottles once home. They have an identification ring near the cap with labels such as lotion, shampoo, conditioner, etc. so that even if your bottles are the same color, you can tell what's in them. Inside the hard cap is a soft membrane that holds the product inside the bottle, and also acts as a pressure release valve, so that as you change elevation, your product doesn't escape all over your luggage. I was easily able to fit 4 of these into the quart size bag that the TSA allows through airport security,(it may even have been possible to fit a fifth). I can't imagine ever traveling without these bottles again.