Blue dragonhide (aka blue d'hide by tanners) is dropped 100% of the time when a Blue Dragon dies. Players can take it to a tanner and turn it into blue dragon leather for a fee of 20 coins per hide. Players can make blue d'hide armour from the leather using the required level from the Crafting skill. A tanner can be found in Lumbridge just south of the yaks.
Some items you can make with blue dragonhide
All of these items require 50 Ranged but the body is the only item that requires 40 Defence.
At level 66 Crafting you earn the ability to make blue d'hide vambraces.
At level 68 Crafting you earn the ability to make blue d'hide chaps.
At level 71 Crafting you earn the ability to make the blue d'hide body.