Real Steel laser tarettting system from TDI Arms.  Bought it about 10 years ago, so not even sure that TDI Arms make the tri rails any more.

The laser module and mount fit on a standard 20mm rail system.

The laser has a push button remote permanently attached.

The tri-rail attaches to the front sightpost of an M4 style rifle, to give a rail directly over the barrel and two side rails on the sightpost.

The barrel rail gives a red dot directly aligned with the barrel - quite useful!

NOTE : As this is real steel, it will NOT fit on a standard TM AEG or similar.  It is designed to fit the specifications of a real front sightpost.

The image showing it mounted is on my PTW, so it should fit similar weapon systems. 

Looking for £50 + £5 P&P