While regular Gundam model lines strive for realism by introducing High Grade, Master Grade, and Perfect Grade models, SD Gundam models are designed for (and sometimes by) the customization crowd. Many SD Gundam models are designed such that variations of the stock models, as seen by SD Gundam comics, can be made by using parts from other SD Gundam kits. Modifying SD models is very popular in Japan, more so than the full-sized counterparts. In addition to made-up robots contributed to SD Gundam comics, Bandai also held monthly contests for custom Gundam (usually Musha-based) models.