After market kits are add ons to a main kit, meant to increase detail and correct incocities in the original kit. These kits come in many forms, but the most common materials used are white metal, resin and photoetched metal. Cast metal is typically used in replacement pats or to add small details, including main gun barrels and machine guns for armour models and wheel struts on aircraft. White metal has recently fallen out of favor on aftermarket kits in favor of resin. Resin pieces of models are typically produced either through molding or 3d printing. It is valued for its ability to hold crisp detail and be modified. Tires for vehicles, heads for figures, and assorted other details are available in resin. Photoetch is perhaps the most prevalent form of aftermarket goods, appearing in most detail kits and some full models. It consists of thin sheets of brass or nickel that have been laser etched into a firm yet bendable and highly detailed part. Given its versatility, photoetch is used in everything from seatbelts on aircraft to engine grilles on armored vehicles.