Feature:
Breathing exercise equipment to challenge yourself for better exercise and improve overall endurance.
Vital capacity - it helps to expand and improve vital capacity without the risk of having to do a lot of aerobic exercise and burning calories.
The portable device - lung breathing training instrument is very compact. Easy to carry.
The adjustable resistance dial makes the simplest task more difficult, and can exercise more intensely according to your needs.

Specification:
Material: silicone