Mailer box are not pre glued, side boarders are moved to get the box ready to use. Theses boxes are mostly used for havier products due to its sturdy structure. The extra front panel is stretched out with two cherry locks at both ends which gives more sturdy structure. These boxes are delivered in a flat shape and client need to assemble them. It saves a lot of time and effort because of very easy to assembly process. These boxes can be produced with any customization in any custom size!