Belt of Inertial Barrier gives the wearer of the Belt a +5 bonus to saving throws vs. breath, 25% resistance missiles and a 50% resistance to magical damage (this is not the same as 50% resistance to magic), which makes it a very useful and valuable girdle, and it can be used by all classes, except Kensai and wizard slayers. It has a weight of 2 lbs and it appears in Baldur's Gate II: Shadows of Amn, where it's sold by an unnamed merchant in Trademeet after the genie problem is sorted out.
When worn, this belt creates a dense curtain of air around the wearer. This curtain, or barrier provides superior protection against breath attacks as well as magic. By the scorch marks on the worn leather, it is obvious that this belt has been worn at least once against a dragon.