The STY-550 SD is an alternative needle (replacement needle) that performs as the original needle, not the factory needles produced by the manufacturer for use with SHARP (Optonica) record cartridges. This replacement needle is a "synthetic diamond needle" type. This is a generic model that plays a regular range of sound ranges, with a standard conical shape. General life is about 200 hours. The successor to the SP.50-550 STY-550 GRN (4951586393702).