Race restriction

A race restricted item can only be used by the specified race or a character with sufficient Use Magic Device ability. A race restricted item has a minimum level restriction two lower than non-restricted version of the same item.
 * e.g. a Helm of Intimidation +7 has a minimum level restriction of 7, a Helm of Intimidation +7 for dwarves only has a minimum level restriction of 5.

If you are using a race restricted item with UMD you only have to achieve the required umd when you equip the item. (You can use Eagle's Splendor spell buff, ability boosts or a number of other things to equip the item). If your UMD is not high enough to use your equipped gear when you log in, the gear will be in your inventory.

Equipment can also be restricted by alignment.