The Reference Series of wooden cartridges are a fixed coil design, hand-crafted at Grado labs from a specially selected species of mahogany. An intricate procedure of curing is done between production steps to achieve optimal sonic quality. This series generator/stylus module is not replaceable* allowing a redesigned one-piece magnetic circuit and a reduction of chassis resonances. The Reference Series utilizes manufacturing and assembly techniques of fantastic accuracy and precision, and the result is virtual perfection. Should be used only with the finest equipment. Recommended tracking force 3/4 to 2 grams.