If you use an SRM power meter with your Hollowgram crankset, you'll need to use the modified spindle and left bearing shield. Cannondale modifies a standard bearing shield and spindle to give needed clearance between the SRM electronics and the BB shell on the frame. It effectively moves the crankset about 1.5mm to the drive side.
SRM bearing shield is for left only. Use a standard shield for the drive side. Must be used with modified spindle for SRM.