Police Department Trade in FLIR T50 ACTS (Advanced Combat Thermosight) Clip on Thermal Imaging Weaponsight. These were a collaboration between FLIR and Trijicon and were designed to mount in front of an ACOG. These can be mounted in front most optics but were specifically designed for use with the ACOG. They can also be used a stand alone weaponsight or a hand held veiwer. These also include a Class III IR aiming laser. Excellent value when you receive a laser and thermal sight.

Here is a nice review of the sight:
http://www.thefirearmblog.com/blog/2018/02/28/flir-t50/...