What you are purchasing here are 38 by 28mm (Layflat Dimensions) tamper seal shrink bands that work best for small boston round bottles, vials, dropper bottles, roll-on bottles and more. Directions: Place shrink band around the lid of the bottle that you will be shrinking it to. Apply heat with the use of a heat gun or heat tunnel. I don't recommend using a blow dryer; it's possible but not worth it unless you're only doing a small quantity of bottles. The shrink bands are easy to heat and durable. Have any questions at all about the shrink bands? Just send me a message and I'll get back to you as soon as I can!