How to measure your Scroll Wheel Encoder
If you are not sure of the Scroll Wheel Encoder size needed for your Mouse, it is best to measure the height of the current Encoder. Many Encoders will have a number stamped on the face plate. As an example a Scroll Wheel Encoder stamped with a 9 is 9mm. If there is no number stamped on the face plate then you will need to measure it yourself, this can be done with a metric ruler or dial calipers
To measure the height of your Scroll Wheel Encoder, you need to take a measurement from the base of the mounting plate to the center of the Encoder wheel holder.