Royal Mail PIP Large Letter EcoFriendly Cardboard Postal Mail Box C4 C5 C6 DL
C4 Die-cut 322 x 229 x 20mm Large Letter. C5 Die-cut 220 x 160 x 20mm Large Letter. C6 Die-cut 160 x 110 x 20mm Large Letter. These Sizes are also designed to fit A4, A5, A6, DL letter sizes to make it easy to get the right size for you.