We find that the caps on many of the plastic vials used in survival kits always fall off. So, we had these food grade Screw Top Plastic Vials made especially for us. Great for survival kits, they are shorter than our Mini Plastic Vials (21042), but larger around. They are great for storing various small items in your survival kit and are really handy for a small fishing tackle kit. The caps screw on (so they don't fall off in your kit) and are made of black metal. These vials Are Not waterproof. They measure 2-1/2" long (2-3/8" usable length inside) x 5/8" diameter. Packages 3 vials to a bag.