The 4192, also known as JMC 4192, is a square drive tuning tool designed for the precise adjustment of Johanson trimmer capacitors. It features a 0.025-inch (0.635 mm) square drive tip that ensures a captive, non-slip fit for tamper-proof adjustments. This tool is compatible with several Johanson trimmer series, including the Thin-Trim® (9701, 9702 series), Cera-Trim® (2322 series), and Seal-Trim® (9820 series).