Guild Wars 2

You can transmute it on to other back items (so I am told, I have not used my wings yet). If you put it on a soulbound item, it will be soulbound. Skins, however, are always transferable to new items of the same type, and there are things to do (costing 2 transmutes) to convert them from soulbound to account bound.

I have 3 of them from drops.

1)You can use them in combat.
2)One time ability means when you transmute the dragonwing skin item onto a backpiece, the item will be gone. You will have to use transmutation crystals to move the skin from item to item after that.

One time ability also means you only have one copy of the wings.

Once you apply the skin to an item it becomes the same as any other back item. You can use transmutation stones or crystals to transfer the skin to another item but you can’t make copies. If you want 2 characters to have the wings, or want 2 sets with different stats or whatever you will need to find or buy another set of wings.