A revolution in personal fit, SmartFit SMF30 from Howard Leight uses Conforming Material Technology (CMT) to adapt its shape to the unique shape of the ear canal. The warmth inside your ear canal helps to mold (temporarily) the ear plug to your unique shape. Once removed, the earplug reverts to its original shape. This helps deliver superior comfort and a truly individual fit, which is unusual in a reusable earplug. With one plug that fits most ear canals you don't need multiple sizes, which keeps inventory management to a minimum. The SmartFit earplugs come in the Howard Leight HearPack reusable plastic clamshell storage case. A detachable cord system means you get corded and un-corded plugs in one item. Just remove the cord by pulling it out of the plug. It may be replaced back into the plug at any time. The SmartFit earplug has an NRR25 rating. Sold in a box of 100 pairs.