One band. Each strength band is a single loop of stretchy latex that can be used in a few ways:
1. To add resistance to exercises in a resistance curve. On an exercise such as the bench press, if you wrap the band arou the bar and any suitable attachment point below it, the top portion of your lift will become harder. Many people struggle mainly in the beginning (lower) part of the lift, and adding bands to the bar helps make the upper part of the lift more difficult. Adding a resistance curve helps intermediate and advanced lifters push through plateaus in their training.
2. To assist in exercises where you can't complete enough reps unassisted, such as pull ups or dips. With pull ups, the band is looped over the pull up bar and you stand on it or put a knee through it. This effectively reduces your weight resistance, enabling you to complete more reps. Dips can be done similarly, wrapping the band around the dip bars.
3. Stretching. You can stretch a lot of different muscles by looping the band around your feet and body in different ways.
All bands are 41" in length. Five different widths provide a range of resistance levels.
1/2" wide (orange)
Primarily used for stretching and doing warm up exercises. Resistance when stretched to 2x length is 20 lbs.
3/4" wide (green)
Similar to above. Resistance when stretched to 2x length is 35 lbs.
1 1/8" wide (red)
Good choice as a general use band and a specifically for adding resistance to people under 140 pounds during walks, high knees, or sprints. Resistance when stretched to 2x length is 60 lbs.
1 3/4" wide (blue)
This band is also a good size for general use and for adding resistance to people from 140 to 200 pounds for body movements. Good choice for pull up training. Resistance when stretched to 2x length is 75 lbs.
2 1/2" wide (black)
For making bodyweight pull ups a lot easier, or for adding a resistance curve for barbell training. Resistance when stretched to 2x length is 135 lbs.
Note that these colors are not standardized. If you have bands of another brand you want to match, check the length and width.