This model was custom designed for the M4A1 as sold to the US Special Forces. Unit comes with a flattop rail adapter. Additions to the original that are now standard with all reflex include dust cover and polarizing filter. Trijicons technologically advanced Reflex sights offer shooters the perfect combination of speed and precision under virtually any lighting conditions.
With the 10% discount this item comes to 446.36 + 5.00 shipping.
Flint Rock, I sent a reply to your request, but don't see my reply in the thread. Kind of new to this site. Anyway, the life span is 15 yrs. If you send back your sight to Trijicon they can replace tritium for 135 dollars.