Choosing the length may be the hardest part about building your braid. Understand that this displayed image is an assumption of how long it will be on a client. If you are short, 14" may look like 16" on you, or vice versa. Be sure to keep that in mind.
Bob (10") - Burned ends, blunt cut.
Bra (16") - Long enough to put into a bun, easier to style when down.
Waist (20") - Most popular, great for all styles.
Butt (24") - Holds a little weight, great for all styles.
Thigh (30") - Statement braids, holds some weight, looks great down.