38 x 28 mm clear perforated shrink band for small boston round bottles, vials, dropper bottles, roll-on bottles and more. [compatible diameter range: 1/2" – 7/8”] - bundle of 250 supplement and supply 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!