The correct size and strength of envelope to be used for each particular postal situation will be determined by the type of enclosures to be mailed.
Size - the envelope must properly accomodate the insert(s).
- If the envelope is too large, the inserts will slide causing an imbalance that can rip the envelope, losing contents. A snug fit keeps enclosures firm in the envelope.
- Conversely, if the envelope is overstuffed, it can burts at the seams, resulting in a total loss of contents.
Strength - the envelope must be strong enought to withstand the weight. If there are sharp edges inside, or stress at the seams from overloading, the envelope can burst, again resulting in loss of contents.