These small bottles are perfect for traveling with, or carrying in a purse or briefcase. Each bottle contains one half-ounce (0.5 oz;15ml) of solution. Design is durable yet allows you to squeeze out one drop at a time. Solution will not damage the item you are testing. Quick & easy to use; instructions included. A MUST-HAVE for anyone who invests in gold. Set also includes a box of five professional quality black pro stones (testing stones) by PuriTEST. Each stone features non-slip-grip rubber backing to hold stone in place as you test. Excellent tools. Excellent value. Great gift idea.