SH series silent modules found in more up market models such as Uprights P116, P121, U1, U3, YUS1, YUS3, YUS5, SE122, SE132, SU7 and Grand S3X, S5X, S6X, S7X, C1X, C2X, C3X, C3X Chrome, C5X, C6X, GC1 and GC2. SC series found in Upright B1,B2,B3 and Grand GB1K - 'entry level' models. Silent piano system silencer & optical sensor, with PCM sound & MIDI recorder unit