Voltronics / Knowles Non-Magnetic PTFE High Voltage Trimmers are designed for applications requiring greater capacitance and voltage ratings than the popular smaller trimmers without the large size and expense of vacuum capacitors. Voltronics / Knowles Non-Magnetic PTFE High Voltage Trimmers feature a non-rotating piston, long life, and no tuning noise. The NMNT series is extremely stable under shock and vibration, and the screw head does not move in and out.