The size of a standard number 10 envelope is 4 1/8 inches high by 9 1/2 inches long.
Why neither of these measurements are ten inches and it is called a #10 envelope is another conversation entirely. It is true that in our business there is no standard #10 envelope.
Most business correspondence that travel through the postal service are #10s. Monthly statements, monthly bills and utility bills (commonly referred to as “transactional” mail) are frequently mailed in a range of other sized envelopes. Direct mail and policy renewals from insurance companies will often use a #10 as well. Fold up an 8-1/2 by 11-inch sheet of paper and you will see that a #10 envelope is its perfect home.
The images of the envelopes needs to be corrected. The return address it too close to the top.