Tadiran TL-5903/S and 15-5903-21500 lithium battery.
We buy these for our Honeywell HC900 controller. They work without issue. Only reason for 4 stars is battery life (about 3.5 months of non-continuous use), but that may be the fault of the controller over the battery itself. Could be a case of "your mileage may vary'. We are investigating that with Honeywell.
Batteries arrived in expected time frame. Put them in the device. Unit is happy with batteries. All is good. Will buy again.