Review (4/5): Great for keeping your brushes clean
These are great for travel to keep your brush heads clean before you use them, and the rest of your bag clean after. They have a slit vent at the end for sanitary purposes, and slide on/off easily. The smaller ones work great for your smallest brushes (think eyeliner and concealer), or silicone lip applicators. For that purpose, they also suction to the lid of your lip product, although they don't stay very firmly attached.