The Size of its inhabitants

Abu Hurairah (radiAllahu anhu) narrated that the Messenger of Allah (salAllahu alayhi wasalam) said: "The molar tooth of an unbeliever or the canine tooth of an unbeliever will be like [Mount] Uhud, and the thickness of his skin will be like a three night's journey."
[Muslim]

Abu Hurairah (radiAllahu anhu) that the Messenger of Allah (salAllahu alayhi wasalam) said: "The distance between the two shoulders of the non-believer in Hell will be like a three day's journey for a swift rider."
[Muslim]

Abu Hurairah (radiAllahu anhu) reported that the Prophet (salAllahu alayhi wasalam) said: "Indeed, the thickness of the disbeliever's skin will be the length of forty-two forearms of those of giants, his molar tooth like [Mount] Uhud, and his seat in Hellfire [the distance] between Makkah and Madinah."
[at-Tirmidhi and al-Hakim]