Although the great helm offered vastly superior protection than previous helmets, such as the nasal helm and spangenhelm, it limited the wearer's peripheral vision, and in addition to being heavy, the mass-produced form (flat-topped without ventilation holes) provided little ventilation and could quickly overheat in hot weather. Knights usually wore the great helm over a mail coif (hood) sometimes in conjunction with a close-fitting iron skull cap known as a cervelliere. The later development of the cervelliere, the bascinet, was also worn beneath the great helm; men-at-arms would often remove the great helm after the first clash of lances, for greater vision and freedom of movement in melee combat. The bascinet had a mail curtain attached, a camail or aventail, which superseded the coif. Mail throat and neck defences such as these were made obsolete when plate gorgets were introduced, around 1400.