Morrowind:Bound Items

Summons a magical Daedric weapon or armor piece.  This automatically becomes equipped (and drawn in the case of a weapon) and replaces any other item you had in that equipment slot.  When the spell expires, that item will be re-equipped and the Bound item will disappear.  Bound items have the same stats as Daedric items of the same type, save that they are weightless, and each has a built-in Constant Effect enchantment on it which fortifies a skill or attribute related to that item.  Bound Items may not be dropped, sold, or given to other people. 

Bound Armor increases the player's Light Armor skill when struck, but the armor itself always provides defense as if the player had an Armor Skill of 30.

Notes
There are several item types which don't have an accompanying Bound Item spell, including crossbows, pauldrons, and greaves.
Bound items can become damaged just like regular items. They rarely break, since the spell usually runs out first (unless you're using a Constant Effect enchantment; see below).  A damaged Bound Item is instantly repaired merely by de-equipping and re-equipping it. 
If, however, you use Armorer skill (your own or an NPC's) to directly repair a Bound Item before the spell expires, you may end up with a permanent duplicate of the Bound Item.  A Bound Item glitched in this way cannot be dropped, sold, or repaired again. However, it is weightless, so it won't encumber you.  It cannot even be deleted from the savegame file without triggering a bug that roots the player character to the spot and causes the character's model to vanish altogether. Only the   console command will successfully eliminate such a glitched Bound Item.
 
Oddly enough, the Bound Dagger has the speed of a Daedric Dagger, and the damage of a Daedric Tanto, making it a superior choice over either of the two for a character using Short Blades as a main source of damage.
It is possible to enchant items with Constant Effect Bound Item.  These will give you the Bound Item whenever the enchanted item is worn.  Jewelry, clothing, pauldrons, and greaves are the best items to enchant with Bound Item effects. Three things to keep in mind:
Avoid use of Armorer skill to repair a Constant Effect Bound Item, as with temporary ones (see above).
Never enchant an item with a Bound Item Constant Effect which will replace itself when worn.  For example, do not enchant a helm with a Constant Effect Bound Helm spell on it.  Wearing such an item will also cause an unrepairable Bound Item to be permanently in your inventory, as with Armorer-repaired ones. 
Because a Bound Item replaces an equivalent other item, an equally bad idea is two items which cancel each other out. For example, a helm with Bound Cuirass and a cuirass with Bound Helm enchantments should never be worn at the same time. It will also be useless to have gauntlets with a Constant Effect of Light and boots with Constant Effect Bound Gauntlets if you want the Light to work (the Light enchantment is on the real gauntlets you are now just carrying around, not on the Bound Gauntlets the enchanted boots have you actually wearing).
Due to a typo, the bound version of the helm is called "Bound_Helm" instead of "Bound Helm".
 

Bound Weapons

Bound Armor