Hall sensor question

Hi All, http://www.aliexpress.com/item/Hall-Sensor-Magnetic-Module-Field-Detecting-Sensor-For-Arduino-Smart-Car-FreeShipping-Dropshipping/653186357.html I have tested these Hall sensors up to 4000rpm - and using the digital out, they are perfect. I verified the accuracy using a 40 RPM motor and I constantly got 40RPM. The module works well, but it's not industrial quality, so I was looking at these http://www.aliexpress.com/item/Hall-Sensor-NJK-5002D-12mm-diameter-detective-distance-10mm-DC6V-DC36V-NPN-3-wire-NC/485081945.html,

but, they say DC6V as the lowest voltage. I'm trying to stick to 5V and lower. Is there something that I am missing here?