This is a multi-strength product,  the product is designed for exercise use on different parts of the body. Generally, Green and Blue are for upper body workout (light resistance) and Yellow, Red and Black for lower body workouts.  The more combination of colours you add the greater the resistance strength of the band (Black being the strongest).

• High end training Resistance Band Fitness Exercise Bands . iThinkProducts 12″ by 2″ heavy duty resistance loop bands are made of latex –  TPE – and come in 5 varying resistance levels. This makes them perfect whether you are just starting to workout, muscle training or a seasoned workout warrior.
• Great with any exercise workout. This resistance band set can be integrated seamlessly with every popular workout program including Yoga, Pilates, and more. Or use them for general exercise, stretching, muscle/strength training, power weight programs.
• Multiple uses. These resistance bands are often used for sports and fitness, physical therapists love these physical therapy bands to help them rehabilitate their patients. Our stretch bands work for people suffering from leg, knee and back injuries.
• Superior quality. Our exercise resistance bands are easy on skin.