Set of two wheels.

11 teeth.

Fits these, among others:

5700, 5600, 5501, 5500, 4500, 4400, 3400, 3300, M662, M601, M600, M592, M591, M581, M580, M571, M570, M531, M530, M511, M512, M430, M330, T661, T400, T300, F800, F700, C810, MC20, MC18, CT-S500