It is crazy but I suppose it is worth the extra security Royal Mail are so poor and bend everything I have had things come completely ripped to pieces!

I know it sounds ridiculous, but that tiny difference in the thickness is what makes the change. In the eyes of the Royal Mail, anything over 5 mm (.2 inches) thick is regarded as a package.

I don't get that as the cardboard doesn't make it any thicker or bigger? and probably not that much heavier.

The ones that have only one Global Stamp on them belong to the brave souls who send their requests with no cardboard. Doing it that way allows the Postal Service to acknowledge it as an "envelope", rather than a "package" (which is considerably cheaper). In the end, it's your choice, but I wouldn't recommend it!

Blimey I didn't expect it to be that expensive I have seen loads from the USA and they only have one on I was just making sure. It will be for Nancy Cartwright does that help at all?

The reason I asked about the cardboard is due to the fact that the envelope may then be recognized as a package when going overseas. So, it could be as high as $10 that you'll need to spend (about 9 stamps). However, you should be good with 5 or 6 of them, since I've found that that rarely occurs

Well, Global Forever stamps are worth $1.15 now.

You should know the weight of your letter to find out how many you should use. The current prices are:

Non-standard and Oversize Lettermail
$4.16 | Up to 3 ounces (=ca 85 g)
$5.10 | Up to 4 ounces (=ca 115 g)
$6.04 | Up to 5 ounces (=ca 141 g)
$6.97 | Up to 6 ounces (=ca 170 g)

So if your return letter will weight, let's say, 90 grams, then you should apply $5.10, but if you have only Global Forever stamps, then you'll have to spend a bit more: 5x1,15=5.75

Anybody?

Yeah going to be a 'please do not bend' envelope.

It depends... is there cardboard in it?