45 x 23 mm clear perforated shrink bands fits cap diameter 3/4 to 1 inch bundle of 250 supplement and supply what you are purchasing here are 45 by 23mm (layflat dimensions) tamper seal shrink bands that work best for various boston round bottles, tinctures, and many other liquid bottles. 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!