MATERIAL: Made of high quality silicone material, which is non-toxic, odorless, harmless and environmentally friendly, safe for you to use. Respiratory muscle trainer: Treat airway trainer like a lung fitness center.. Train lungs and breathing muscles to improve lung capacity and endurance. Portable: size 3.94 x 2.17 x 1.38 inches (10 x 5.5 x 3.5cm), light and small, convenient to carry. Versatile, easy to use: suitable for many like swimming, diving, surfing, running, fitness, traveling, etc Our products are durable and easy to use. It matches all mouth shapes, can be perfectly sealed, and is convenient to use. Amount adjustment; air you bring: breathing trainer can adjust amount the air you breathe in, improving your daily respiratory health and increasing stamina and vital capacity. The breathing trainer uses a multi-level resistance wheel to reduce the amount of airflow through the lungs and forces you to breathe more focused and deeper. Note: Manual measurement, please allow slight errors on size.. Colors may exist slight difference due to different monitors..< /p> Package including 2 x Silicone Breathing Trainer Note: The data is manual measurement, please allow 1-38cm error , due to differences between light and screen, there will be a certain color difference, the specific received in kind prevail.