Use these white cardboard envelopes to send your products with peace of mind thanks to tamper evident locking flaps, which once inserted can not be opened without causing considerable damage to the cardboard envelope. For extra security, double seal the envelope with one of our packaging tapes. Each white cardboard envelope with locking flaps is manufactured from 380 gsm micro-flute corrugated board which helps maintain the structure & rigidity of the envelope. This keeps your products flat & free from creasing during posting & will protect from day to day wear & tear. Use white cardboard envelopes to improve the presentation of your products & give your products an attractive finish. Extra protection for your products as these cardboard envelopes have reinforced corners to prevent damage to the goods inside. The expandable edges allow the cardboard envelope to increase in height by up to 40 mm, meaning that you can use these cardboard envelopes to post a variety of different proudcts including, DVDs, CDs, books, catalogues & calendars. Sold in packs of white cardboard envelopes. How to choose the correct size white cardboard envelope your your product: When the cardboard envelope is expanded, please note that envelope decreases in opening & length measurements. To use at minimum capacity: Subtract 20 mm from the opening & 10 mm from the length. To use at maximum capacity: Subtract 60 mm from the opening & 30 mm from the length