1. It plays a better airtight role, and the inner cover and bottle are tightly buckled, which not only reduces the entry of air and water vapor, but also reduces the volatilization of the reagents in the bottle and prevents the reagents from deteriorating;
2. The inner cover is relatively tight, which can prevent the leakage of the reagent, but it is a secondary protection for the reagent;
3. The materials of the inner cover and the outer cover are also different, which is more resistant to reagents and more anti-corrosion;
4. An extra layer of inner cover is less likely to be contaminated. The main purpose is to prevent the leakage/deterioration of reagents.