Smooth white All Board Envelopes, they are square with dimensions 164mm x 164mm and designed to match the Royal Mail’s Postage in Proportion guide. These smart-looking board envelopes are manufactured from premium grade 500 micron, 350gsm, GD2 fully coated chipboard. They include an easy-to-use peel and seal strip on a pre-folded flap for easy closing and are the trusted way to keep paper, card and slim items protected during despatch. The smooth outer means labels stick well and you can also print direct onto the surface.