Nature First premium quality strong 150gsm weight white envelopes, made from 100% recycled paper FSC-certified. C4 envelopes measure 229mm x 324mm, to take a sheet on unfolded A4 paper, and these also have a 25mm expanded gusset along the side, ending with a V shaped bottom seam. The peel and seal closure is formed from a longlife hot melt adhesive. They also have a blue internal hatch and are printed with the FSC logo and Recycled text. The window of the envelopes measures 10mm x 105mm, and is positioned 213mm up and 24mm left from the bottom left corner. The window is made from degradable PLA starch based plastic.