Airsoft guns are air or gas powered firearms that fire small spherical plastic pellets of either 6 mm or 8 mm diameter. They are used in the sport of Airsoft which is similar to Paintball.

This is a full size Ak-47 made by Tokyo Marui

Generally they are replicas (in appearance only) of real firearms, but occasionally also fictional firearms the M4 pulse rifle from the aliens films

On occasion airsoft guns can be such perfect replicas that they break certain copyrights, most notably the trademarks of Colt or Heckler & Koch on Tokyo Marui weapons that disallows such trademarks to remain on the gun for import into the United States. Certain companies such as Classic Army or ICS have avoided this problem by licensing their replicas from the original manufacturers like ArmaLite or Olympic Arms.

This is a Stinger R36 made by Crosman

Because airsoft guns are such good replicas they are often used as movie props.

While in essence the three types of airsoft guns, spring, gas, and electric, all work on the same principal of gas pressure being built up in a piston that forces a BB down the gun's barrel, each operation has its own advantages and disadvantages.

Airsoft replicas may be made of metal, plastic, or, most often, a combination of the two. Airsoft replicas (also commonly called "airsoft guns") usually fire 6 mm or 8 mm spherical projectiles (known as "BB"s). BBs are available in many different weights ranging from 0.12 grams to 0.88 grams, but the most commonly used weights are 0.2 gram and 0.25 gram weights selected for their good combinations of range and accuracy. (lighter BBs generally travel further overall, but are more affected by wind, resulting in less overall accuracy at a given distance.) Tokyo Marui AEGs and spring shotguns have their hop up factory-set for .25g bbs. For Extreme Military Simulation (Mil-Sim) some types of .15g .55 rubber ammunition is made, but is very scarce, and almost all have seams, leading to more inaccuracy.