The right fit of helmet
Look for these elements in a helmet:

It should comfortably touch your head all the way around.

It should be level on your head.

It should extend as low as possible to help cover the sides of your head.

It should be stable enough to resist violent shakes or hard blows and stay in place.

It shouldn’t rock back and forth more than an inch or so. (If you can tilt a helmet while someone is wearing it, then something’s wrong.)

It should protect your forehead. The helmet should be only one to two finger widths above your eyebrows or eyeglass frames.