I use these to mail out brochures and a letter to people. A 8.5x11 folds perfectly in half to fit inside and a few trifold brochures are perfect. It doesn't require extra postage due to the size. Its the biggest envelope you can use without needing extra postage. With a few brochures it does increase the weight so it does take a 65 cent stamp for me to mail but if i just put one brochure it would just be 45 cents. Hope this helps.
I use it to mail flyers. Only need to fold an 8-1/2 X 11 flyer in half. Most important...no extra postage for larger envelope. White looks good with my color flyers too.