From the RuneScape Wiki, the wiki for all things RuneScape

Armadyl chestplate

Release date	28 August 2007 (Update)
Members only?	Yes
Quest item?	No
Tradeable?	Yes
Equipable?	Yes
Stacks?	No
High Alchemy	36,000 coins
Low Alchemy	24,000 coins
Destroy	Drop
Store price	Not sold
Exchange price	18,300,000 coins update
GE Database	Look up price
Examine	A chestplate of great craftsmanship
Weight	4 kg
Click to enlarge

The Armadyl Chestplate is a drop from the Kree'arra and the bodyguards. It, along with the Armadyl helmet and Armadyl plateskirt, is part of the Armadyl armour set. The chestplate is statistically superior to every other torso ranged armour other than Morrigan's leather body, but this armour doesn't degrade making it a more common choice. This makes it the best possible torso armour for rangers that doesn't degrade. The prayer bonus also makes it desirable for the Fight Caves minigame.

Bonuses Hover over image for type												A female and male player wearing full Armadyl armour with the chestplate on the torso
Attack bonus
-7		-7		-7		-15		+33
Defence bonus
+56		+48		+61		+70		+57		+52
Other bonuses
0			0			+1			0
Item compare not supported

Trivia

• Upon the release of RuneScape HD the Armadyl Chestplate was given a slight graphical update. This resulted in a "crop-top" style for male players, exposing the stomach. Needless to say, this change was intended and was not a glitch. The style has since been changed again.
• On 8 July 2009, the chestplate had an update (mentioned in Patch Notes 08/07/09) with the release of Mobilising Armies. It seems to be like it was before the HD update, covering the player's stomach on male characters, but exposing the stomach on female characters.
• Despite being made of metal, it has a superior magic defence bonus.