Hearing protectors fall generally into three categories, including protectors that cap the entrance to the ear canal; protectors which enter the ear canal and seal the ear canal prior to the bend in the ear canal (usually referred to simply as semi-insert devices); and protectors that enter the ear canal and take the bend in the ear canal (sometimes referred to as banded earplugs). Semi-insert hearing protectors generally protect similarly to earplugs, but usually to a lesser level. Semi-insert hearing protectors are also referred to as semi-aural hearing protectors. Semi-insert hearing protectors which enter the ear canal to a greater degree offer better protection but are somewhat less comfortable than those which simply cap the ear. Products which cap the ear have some of the attributes of both earplugs and earmuffs. Typically, they are used for intermittent noise exposures where lighter weight and improved low frequency attenuation are desirable. Hearing protection devices (hpd) such as earmuffs and earplugs can be an effective measure to protect hearing in noisy work environments. However, hearing protection devices are only effective if they are properly sized and carefully fitted into or over the ear. The two common hpd categories are earplugs and earmuffs. There are several common types of hearing protection devices: formable earplugs made of expandable foam. One size fits most people. Pre molded earplugs made from flexible plastics. Often sold in different sizes, they should be selected to provide best fit for each ear. Semi-aural devices or canal caps consist of flexible tips on a lightweight headband. They provide less protection than earplugs or earmuffs but may be good for intermittent use.