Several vehicles allow investors to own bullion indirectly. The investor owns shares in a vehicle that is the direct owner of bullion. The most popular such vehicles are exchange traded funds (ETF) that hold assets and issue shares that are traded on the stock exchange. Large broker dealers (the Authorized Participants) act as market makers and make sure the shares trade at the net asset value. Other vehicles are mutual fund structures with a distinction as to who provides the custody of the metal: a bank or a non-bank custodian.