The Bobcat® T-64, T-66, and T-76 are all built on the same undercarriage platform. Most of the parts are interchangeable with only a few variations to the T-76 considering the track is longer for more footprint and less ground pressure.
There are serial breaks and there are optional styles such as the solid mount versus the torsion, or suspension type undercarriage. The parts are not interchangeable across those two undercarriage styles so you must verify before ordering online. This specific category for the T-66 model is designed for serial numbers B51V11001 & ABOVE