A stripper clip (in US parlance) or charger (in UK parlance) is a speedloader that holds several cartridges (usually consisting of 5 or 10 rounds) together in a single unit for easier loading of a firearm's magazine. A stripper clip is used only for loading the magazine and is not necessary for the firearm to function. It is called a 'stripper' clip because, after the bolt is opened and the stripper clip is placed in position (generally by placing it in a slot on either the receiver or bolt), the user presses on the cartridges from above, sliding them down and off the clip, thereby 'stripping' them off the stripper clip and into the magazine. After the magazine is loaded, the stripper clip is often discarded, but some can be reused many times, depending on the total cumulative wear on the individual stripper clip. Depending on the firearm, magazine, and cartridge, stripper clips come in a variety of shapes, some quite complex, though most are either straight or crescent-shaped pieces of stamped metal - usually brass, or steel (often blued) - or plastic.