Gold bullion refers to gold that is in the form of bars or ingots, typically of high purity, often 99.5% or more. It is primarily used as a form of investment or as a reserve asset by central banks. Investors buy gold bullion to protect their wealth against inflation and economic uncertainty. Gold bullion is usually measured in troy ounces, with one standard bar weighing about 400 troy ounces. It is traded on various markets and can be bought from dealers or financial institutions. The value of gold bullion fluctuates based on market demand and the current price of gold.