1. Stack material higher grade / lower temperature rise/ high performance. 2. Commutator copper grad higher and small bar to bar surge lead to lower spark and higher endurance. 3. Copper wire grade 2 endurance for high temperature. 4. Epoxy resin to protect the copper wire from moving to avoid burning for big vibrarion hammer. 5. Shaft mater better on hardness and gear. Different batches may have slight color differences or differences in the actual product, which not affect the use Notice: The color is random, cannot be chosen the specified color. Colour:Photo Color Material:copper+Plastic Package Contents: 1x Armature Rotor Anchor Replacement Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.