This is the replacement rotor for the Aquarium Pharmaceuticals Filstar L (XP3) and Filstar M (XP2). The original L (XP3) rotor was either white or red. This rotor/impeller is the replacement we recommend for the Filstar L (XP3) that was discontinued in 2019. The rotor/impeller assembly includes the rotor/impeller, shaft and 1 rubber bearing. This will produce a slightly smaller flow in most installations. If you want more flow than the original rotor for the L (XP3) then use item 723Q which is the standard rotor for the Filstar XL (XP4).
The rotor is the magnet part of the motor that spins. Attached to this is the impeller which consists of blades that catch and pump the water out of the filter and back to the tank. Over time the rotor magnet loses magnetic strength and will exhibit trouble starting or the filter will have reduced flow even after cleaning. Replace the unit if your filter exhibits these symptoms or if the impeller blades break or separate from the rotor.