Is Bubble Envelope considered a letter?

Question

If I use a bubble envelope the size of 6 in by 4 in, smaller than the size of a normal envelope, is it still consider a letter?. Because I want to mail a toploader in it. if i choose parcel that would cost $1.13, but if i choose letter it would cost $.41 cents. The total weight is less than 1 ounce. SO i want to kno do they still accept it if i mail a bubble envelope (6 by 4 inch) (less than 1 ounce) with a first class stamp 41 cents

Answer 1

You may mail anything 1st class. However, the USPS has additional charges for unusually shaped envelopes. There is a 17 cent surcharge for letters that are not capable of going thru their machines.

Height: 3-1/2 inches to 6-1/8 inches

Length: 5 inches to 11-1/2 inches

Thickness: 0.007 inch 1/4 inch [oops?]

For additional info, click on the link below. Then click the "?" under letter.