There are several things you should keep in mind when you use paper for the outer covering of the mail item.

The paper used for the outer covering of the mail item should:

• Be opaque enough to prevent any printing or graphics from showing through the envelope (we recommend an opacity of 80% or more)
• Not be translucent
• Be smooth (25 to 330 Sheffield Smoothness Units) with no raised areas
• Have a reflectance between 30% and 96%, excluding the 2D barcode quiet zone
• Be clear of:
  • Dark fibres
  • Background patterns
  • Textures
  • Watermarks
• Be clear of fluorescent ink

For more information, refer to Appendix A: Test – Outer cover material.

Optimal card size is 165 mm (length) x 108 mm (width) with paper grain direction long.

Oversize items don’t always need a wrapper.

You may send open items without a wrapper such as:

• Brochures
• Catalogues
• Magazines
• Newspapers

Open items without a wrapper must:

• Be at least 0.5 mm thick and weigh at least 10 g.
• Have cover pages strong enough to withstand machine processing (paper at least twice as thick as the inside pages).
• Be bound along the longest side.
• Be bound so they stay flat and even without bulges. Binding methods such as staples, glue, or stitches are acceptable, but spring spines aren’t, since they cause items to bulge.
• Be the same width as the mail item, not folded to cover only part of it, if you use gatefold covers.