Littelfuse cheat sheet on all varistors related. Link here (PDF)
Transient suppressors can be exposed to high currents for short durations in the nanoseconds to millisecond time frame.
Littelfuse Varistors are connected in parallel to the load, and any voltage drop in the leads to the varistor will reduce its effectiveness. Best results are obtained by using short leads that are close together to reduce induced voltages and a low ohmic resistance to reduce I • R drops.