With a wide range of envelopes to choose from, here is a brief guide to help choose the correct envelope for the correct purpose.Envelopes Weights (GSM)Envelopes can be found in various weight/thicknesses and are measured in Grams per square inch or GSM. In exactly the same way that paper is graded, the greater the gsm of the envelope the thicker the paper/card it is made from.Envelope Sizes Envelopes come in a variety of sizes and are listed in international (ISO) size system. Envelope sizes range from C0 (being the largest) through to C7. The most common envelope sizes are ISO C4, C5 and DL. Below is a description of the dimensions of each envelope to help you decide the best way to send your letters, memos and other documents. • C4 Envelopes – measuring 324x229mm C4 envelopes can hold an unfolded A4 sheet of paper. Ideal for sending reports, brochures and documents on A4 paper that cannot be folded.• C5 Envelopes – measuring 229x162mm C5 envelopes can either an A5 sheet of paper or an A4 sheet of paper folded in half• C6 Envelopes – measuring 114x162mm C6 envelopes will hold an A5 sheet folded in half or an A4 sheet of paper folded twice.• DL Envelopes – measuring 100x220mm DL envelopes will hold a A4 sheet folded twice or an A5 sheet folded once. DL Envelopes are what you typically use for sending letters and what you receive in your daily post.Types of Envelopes• Gummed Envelopes – Traditional “Lick and Stick” envelopes which require you to moisten the adhesive on the flap of the envelopes before pressing and sealing.• Self Seal Envelopes o Press Seal – Fold over the flap of the envelopes and pressing to seal o Peal & Seal – Similar to Press Seal Envelopes but you must first remove a plastic strip to reveal the bonding glue before folding over the flap and pressing down to seal.• Plain Envelopes – Plain envelopes are useful if you are looking for a much more personalised correspondence and as they contain no window the address needs to be written on the envelope. Also useful if you are want to print directly onto the envelope• Windowed envelopes – Windowed envelopes contains a small clear plastic film on the front of the envelope which is used to display the printed address of the letter/document inside. • Manilla/White Envelopes – All our envelopes come in a choice of either white or manila. Manilla is the traditional brown style of envelope that is available.• Board Backed Envelopes – A rigid board within the envelope keeps import and documents safe. Ideal solution when sending photographs.• Padded Envelopes – If you need to send an item –big or small – and require and envelopes which provide much more protection than an standard envelope. Exceptionally strong and tear-resistant, padded envelopes are ideal for bulky or heavy items as well as delicate items such as CD/DVDs. Many of our padded envelopes are also weather resistant.• Recycled Envelopes – If you have concerns about the environmental impact envelopes and other paper supplies have on the environment you need not worry. Most envelopes are now made from recycled content and indicate the percentage of recycled content in three grades – 100% recycled paper, up to 50% recycled and over 50% recycled. You may also notice environmental information on envelopes including whether it is FSC sourced. Here you can find a Guide to Green Office Supplies Labels.