When purchasing a helmet, it is essential to ensure that it **is approved**, which means it has passed quality tests and is safe for use. This is crucial because approved helmets are designed to protect the head in the event of an accident, distributing the impact force and preventing serious injuries.

Additionally, it is important to consider the **size** of the helmet. It should fit well on the head to offer maximum protection. A helmet that does not fit properly may not adequately protect in the event of an accident.

The **material** of the helmet is also relevant. Some materials may lose their properties over time or if paints or stickers are applied to them, which could compromise safety.

Therefore, when choosing a helmet, you should not only check that it is approved but also pay attention to its size and material to ensure maximum safety.