The exterior of the case is approximately 1 1/8 inches long, 3/8 inch diameter. Solid metal. Each holds 7-8 nitroglycerin tablets. Rubber o-ring OR internal gasket seal. 24 inch chain. Has split ring attachment so they can easily be converted to key ring use.
Knowing I was supposed to have nitroglycerin tablets on hand I started a search for something small - really small. I found this necklace and decided to try it. It's very tiny, comes on a chain that slips over my head and holds several nitro tablets securely. It is waterproof as I forgot to take it off once when in the water. When I checked - tablets were dry and safe. It is marked on the outside with a medical sign and what is inside. The canister part is just over 1 1/8" long - add a little more for the part that the chain runs through. Reasonably priced, fast shipping. Very happy with my purchase.