I recently ordered an eye mask, which has 100% silk on it's underside. I know that wearing silk is haram for men, but does an eye mask come under clothing and the amount of fabric is also very less ??
Yes, "eye masks" aka blindfolds are considered garments that are worn. As per Bukhari hadith 5837, silk is prohibited for males in the form of wearing it and in the form of sleeping on it. In your case, it's a little bit of both. Therefore, men should refrain from wearing this item. Gift it to a female relative and find another eye mask that isn't made from 100% pure silk.