I suppose "MR" is a puff marketer's term for a damper using magnetorheological fluid. In that case, the real challenge in distributing or selling aftermarket "MR" shocks is in the control units.

In adjustable-valving applications (like the Tein EDFC) you would need a control unit to vary the electromagnetic field strength based on a user interface and then a power source to maintain the EMF.

In applications like you see in corvettes and audi, you need to interface the shocks with, at minimum, a steering and speed sensor. A higher-quality system would interface with the vehicles ABS, TCS, a roll sensor, steering, speed, suspension travel and yaw sensor.