Abstract: A varistor disk assembly for mounting to a commutator base comprising a non-conductive retaining ring, a conductive member, and a varistor disk interposed between the commutator base and the distal end of the retaining ring. The retaining ring has an axial bore therethrough providing a friction fit with the motor shaft on which the commutator is mounted. A tolerance absorbing member can be interposed between the varistor disk and the retaining ring. The conductive member conducts current through its thickness from the commutator base to the varistor disk, but does not conduct current between adjacent commutator segments. To orient the varistor disk to the commutator, the proximal end of the retaining ring can have at least one planar side formed in its periphery for alignment with one of the commutator segments, while the distal end of the retaining ring also has formed in its periphery a planar side, and the varistor disk is provided with a complementary planar side in its inner diameter.