Bone Leggings

 is a Tailoring craftable item and part of the Bone Armor set that was released in Release 34 as part of a top-tier armor set. From the release notes:
 * Bone Armor, a new type of armor, is crafted at a Tailoring table from bones refined at a Carpentry station (the first armor to involve Carpentry). It has the attributes of Heavy Armor (high Damage Avoidance) but it is actually classified as Light Armor, so when Masterworked, your modifiers will be Light Armor modifiers and your skills used with it will be Light Armor skills. It also has very high durability, making it ideal for Enchanting and Masterworking. However, the bones needed to craft it are exceedingly difficult to acquire. In addition to the normal Tailoring, Carpentry, and Smithing ingredients (leather, cloth, thread, wax, metal etc.) Bone Armor requires parts from Dragons, Phoenixes, Demons, and Tier 5 Skeletons.