This armor seems to weigh less than it should.
When wearing armor that has this property, you can carry up to a medium load as if it were a light load (ignoring the maximum Dexterity bonus, check penalty, and reduced speed normally incurred by a medium load). These reductions apply only to penalties for the load you carry, not to any reduction in speed caused by the armor itself.
In addition, you can walk for up to 10 hours in a day before having to make Constitution checks to avoid taking nonlethal damage (see Forced March).
Prerequisites: Craft Magic Arms and Armor, bear’s endurance.
Cost to Create: 750 gp, 60 XP, 2 days.
Source: Magic Item Compendium, page 10. Previously published in Heroes of Battle, page 129, as “Easy Traveling”.