Folding A4 items will move the item from a "large letter" to a "letter" classification and save on postage
Many "packets" could qualify for cheaper "letter" or "large letter" prices if you keep the thickness to less than 5mm (letter) or 25mm (large letter)
Only available for bulk mail users but often a cheaper option for some items eg parts and samples, books, cylindrical packages
The first price band now extends to 100g instead of 60g. Can you use the additional weight? If you go above 100g think if you can use any additional "free" weight since the price now remains the same up to 250g
Provided you are within the overall dimensions of the format you can still mail round, star shaped or other unusual shape mailers at the same price as a "conventional" shape
Let us handle your printing needs and we can save you as much as 55% on your postage using Royal Mail data sorting techniques!