The X3R32/64 is a recording-only headstage with a base footprint of about 8.5x8.5mm and includes a built-in accelerometer.
The X3SR32 is the stim-record headstage, with a base footprint of about 8.5x8.5mm. The SR X-Headstages do not support accelerometers.
The X6R128 is a recording-only headstage with a base footprint of about 10x10mm and includes a built-in accelerometer.