Trimmer and variable capacitors are a group of devices that provide a capacitance that is user-adjustable within some specified, relatively narrow range. Devices covering capacitance ranges of a few picofarads to a few nanofarads are commonly available, with voltage ratings from the tens of volts into the kilovolts. Typically used for calibration, tuning, and matching applications, their relatively high cost and potential for maladjustment recommends the use of fixed value devices where feasible.