Rock-shell armour (also known as Rockshell armour) is Fremennik armour for warriors that can only be made by going to Waterbirth Island or bought. Additionally, parts of this armour can be dropped by Dagannoth Rex. Due to the swift rise in the price of this armour, it is a lot cheaper to buy the rock-shell pieces and then bring them to Skulgrimen in order to get the armour. However this method might fail because it is quite hard to get rock-shell pieces as they are only dropped by the Dagannoth Rex and giant rock crabs, who are both hard to defeat due to their high combat level and defence. This set of armour cannot be made using the Smithingskill.
The armour is a lower-level Power set, requiring 50 Defence. While wearing the full set of armour (boots and gloves are not needed), the title of "Rockcrusher" is added to the Fremennik name of the player. Since most of the set can only be worn after completing The Fremennik Trials quest, players are advised not to buy it unless they have completed the quest, or plan to do so soon.