Airsoft pellet

Airsoft pellets are spherical projectiles used by airsoft guns. Typically made of plastic, they usually measure around 6 mm (0.24 in) in diameter (though selective models use 8 mm), and weigh 0.12–0.48 g (1.9–7.4 gr) with the most popular weights being 0.12 g, 0.20 g and 0.25 g. While airsofters almost always incorrectly call them "BBs", they are not the same as the 4.5 mm metal projectiles that BB guns fire, nor the 4.6 mm (0.180 in) birdshot size from which the term "BB" originated.

Although the majority of pellets bought and used are simple spherical projectiles made of plastic, some of the following special varieties can be used to give a player an advantage.

Biodegradable pellets are available, and are often required by outdoor fields where sweeping is not an option. Conventional pellets pollute the environment, as most non-biodegradable pellets have a mineral or petroleum-based center, coated in non-biodegradable plastics, thus ensuring they will stay in the environment for several hundred years if not collected. Biodegradable pellets are made of various types of resin, often developed for the agricultural industry, and better makes are certified as compostable. There is a mixture of degradable processes being used, such as soil microbes and photosensitive degradation. Biodegradable pellets are currently being produced with all the characteristics of the best of the conventional, with homogeneous resin construction.

Most high-quality pellets are available in a non-biodegradable version, as well as a biodegradable version that costs slightly more. Both bio- and non-biodegradable pellets are popular and widely available.

Glow-in-the-dark pellets, known as tracer pellets, can be used in conjunction with a device that "charges" the pellets by flashing them with a burst of light before leaving the barrel, so that they remain luminescent in flight for use during nocturnal games/operations. This tracer unit is usually hidden from view, often disguised as a suppressor, or is included inside the magazine or hop-up unit. There are also biodegradable tracer pellets available.

...
Wikipedia