The C5 envelope is a type of envelope that is commonly used for mailing letters, documents, and other flat items. It measures approximately 162 mm x 229 mm (or 6.4 inches x 9 inches) and is designed to accommodate A5 paper, which measures 148 mm x 210 mm (or 5.8 inches x 8.3 inches).
The term "Please do not bend" refers to a particular type of envelope that is designed to prevent the contents from being bent or damaged during the mailing process. These envelopes are typically made from thick, sturdy materials such as cardboard or heavy-duty paper, and are often reinforced with additional layers of padding or cardboard to provide extra protection.
When mailing items in a "Please do not bend" C5 envelope, it is important to ensure that the contents are securely placed inside and that the envelope is properly sealed to prevent any accidental openings during transit.