Each one is made in one piece which opens and closes easily. The integrated closure fastens securely so that it stay shut while being carried. The sizes combine and tuck inside one another which has many practical uses. have hinged cover and flip lock. Note is not liquid tight. Dimensions is Large is 22.5 x 12.1 x 6.8cm high Medium is 13 x 10 x 5cm high Small is 10 x 8.4 x 5.2 cm high.