A cluster of 4 markers that is used to track the motion of a leg joint during a Run3D gait analysis.

The cluster is strapped securely to the back of a client's thigh or calf and is then picked up by the cameras in order to determine the motion of that joint.

Each cluster needs to have a unique configuration, and one that is not rotationally or reflectionally symmetric. The clusters are designed with 7 holes, such that the 4 markers can be placed into different ones to create unique patterns. You might need to move the individual markers around to make sure they don't clash with a pre-owned cluster!