Applications using tantalum capacitors take advantage of their low leakage current, high capacity and long term stability and reliability. For example, they are used in sample and hold circuits which rely on low leakage current to achieve long hold duration. They are also commonly used for power supply filtering on computer motherboards and cell phones due to their small size and long term stability, most often in surface mount form. Tantalum capacitors are also available in military specifications versions (MIL-SPEC), which offer tighter tolerances and a wider operating temperature range. They are a popular replacement for aluminum electrolytics in military applications because they do not tend to dry out and change capacitance over time. Medical electronics also rely on tantalum because of their high stability. Audio amplifiers sometimes use tantalum capacitors where stability is a critical factor.