This should be a product of genius! Most speed sensors have to be fixed on the chassis. Some may not fit the chassis well and we need to cut the chassis a little bit, others may be interfered with other components on the chassis because of the pin, some may even not long enough to reach the encorder. This Opto-Coupler Speed Sensor with Kit, by contrast, does not need to be fixed on the chassis - it was designed to fasten it on the motor. This not only can save more space on the chassis, but also ensure the sensor reach the encorder without any interference! With this photo you will understand why I highly appraise it!

Opto-Coupler Speed Sensor With Kit