Features: It can help increase hand strength, improve grip strength, and improve finger flexibility. Make from silicone materials, rings designs increases frictions, nonslip and enduring. 3 different strength can adjusted, suitable for each training stage. Small and portable, you can exercise hand muscles at any time. Suitable for most people who need to strengthen their hands, such as athlete, Musical Instruments, office worker, etc. Can used at homes, office, gym and other place, convenient and fast, at anytimes to carry out hand strength training. Specifications: Materials: Silicone Color: Pink/Blue/Light Blue/Grey/Black Maximums Diameter: about 8cm/3.15inch Pink grip strength: 20-30-40LB Blue grip strength: 30-40-50LB Light blue grip strength: 40-50-60LB Gray grip strength: 50-60-70LB Black grip strength: 70-80-90LB Package Includes: 1Pc Hand Strengthener Grip Rings note: Please allow 1-2cm errors due to manual measurement, make surely that you not mind before order. Due to difference between different monitors, the picture may not reflect the actual color.