Finding the Flavor of Chocolate. Gregory Ziegler puts a small block of chocolate into a styrofoam bowl and sticks it into the microwave. Soon, a lovely sweet aroma spreads through the air, lending warmth to the otherwise bleak lab. Ziegler takes the bowl out of the microwave; it's filled with a thick, swirling liquid.
First Class Large Envelope/Flat Mail. Minimum size: 6 1/8 inches tall or 11 1/2 inches long and 0.007 inches thick. Maximum size: 12 inches tall x 15 inches long and 3/4 inches thick. Maximum weight: Up to 13 oz.
Quick Answer. The maximum weight for a First-Class letter envelope, which is 3.5 ounces, according to the United States Post Office. There are also size and proportion requirements to consider when sending mail First-Class. Letter envelopes must be rectangular, and they must not exceed 11.5 inches in length or 6.125 inches in height.