With that bit of information you can spell any key containing flats. A key with 5 flats would contain the first 5 flats from the order Bb, Eb, Ab, Db, and Gb. If the key has two flats, it uses the first two flats from the order of flats Bb and Eb. If a key has one flat, it only contains the first flat from the order of flats Bb. This order tells you which notes are flat in a key containing flats. The order of flats is a sequence of seven flat note names.

Since you're always playing in some key, knowing your keys in this manner will always be of great benefit.

Once you have memorized how many sharps or flats are in each key in combination with the order of sharps and flats, you will be able to spell the notes of each key. This order is called the order of flats and the order of sharps. The flats and sharps of each key follow a specific, unchanging order that you need to memorize. The flats and sharps from key to key are not random.

In the lesson about the major keys on the circle of 5ths you learned every key has a unique number of flats or sharps. What is the Order of Sharps and the Order of Flats?

C and e flats