Another trend which has become very extensive is to produce kits where the parts snap together, with no glue needed; sometimes the majority of the parts snap together with a few requiring glue. Often there is some simplification of detail as well; for instance, automotive kits without opening hoods and no engine detail, or sometimes opaque windows with no interior detail. These are often supplied in colored plastic, although smaller details would still require painting. Decals are usually not supplied with these but sometimes vinyl stickers are provided for insignia and similar details.