EN 352-1 – European Safety Standard for Earmuffs/Ear Defenders:

Earmuffs in accordance with standard DIN EN 352-1 are defined as hearing protectors that enclose each of the wearer's external ears with a functional capsule.

As it is often desirable to frequently put on and take off ear protection in areas with variable noise exposure, earmuffs are recommended for such environments.

Here is a link to this Delta Plus ear defender on the manufactures website.