Plastic seals Variable length seals, commonly called "pull tight seals" can fit many applications from securing the neck of a bag or mail sack to sealing chemical drums, first aid kits and fire extinguishers. They have an adjustable length much like a cable tie but offer a much higher security level and an audit trail due to sequential numbering and the ability on some seals to be bar-coded and have a company name and logo printed or laser etched on.

Fixed-length seals tend to be more tamper resistant than variable length as there are no sliding parts, they simply 'click' into place to lock, which can make them easier to fit than variable length seals. Most fixed length seals can also be branded and numbered for extra security. Fixed length is often the choice of single use security seals for transport applications.