Weights are an important form of evidence for Viking Age commerce and the use of standards across the different economic systems within which Vikings were integrated. Many of the weights discovered, particularly ones in Ireland and those of Arabic type, suggest that a standardized system of weights existed in some areas. These standard weights, alongside standard values of silver, are what allowed the bullion economy of Viking occupied areas to function. A bullion economy was a barter economy that relied on the exchange of set amounts of precious metal in various forms, such as arm-rings or coins, for tradable goods, such as food or textiles. Each merchant would have brought their own set of weights and scales to a transaction to make sure that the trade was conducted fairly.