As with any envelope the GSM' dictates the strength and quality to be expected from the envelope, this is no different with Non-Standard sized envelope products.
GSM actually means grams per square metre and is the universally accepted metric for the measurement of paper
This group of
Non-Standard envelopes offers an extremely good range of GSM options from
80gsm envelopes through to
200gsm envelopes.
With the most common sizes being;
90gsm envelopes,
100gsm envelopes,
110gsm envelopes,
115gsm,
150gsm,
125gsm &,
130gsm envelopes in between.

If you have an important task at hand then it is probably worth spending the extra money on some heavier weight envelopes as they are received in better condition and also the extra weight may leave an impression on the recipient.