Voltronics / Knowles J Series Ceramic Chip Trimmer Capacitors outperform all similar trimmers and provide leading stability over time with low capacitance drift. Voltronics / Knowles J Series Ceramic Chip Trimmer Capacitors offer up to 50% higher Q than similar trimmers. J Series Trimmers are usable to over 1GHz and have no exposed metal mechanism underneath the JR and JZ capacitors.