The A-Spec M3 is manufactured to be compatible for uses with a Shield RMS-C® footprint, and it boasts a red auto-brightness control reticle to accommodate shooting at any time, day or night. This optic is perfect for subcompact guns, and is notoriously durable – aluminum alloy housing, IP55 water-resistant, shockproof, able to withstand up to .375 H&H caliber and operate in temperatures from -22F to 122F. With a battery life up to 100,000 hours and an included rubber cover, low-profile fixed mount and manual, the Sightmark micro red dot sight is guaranteed to help you Make Your Mark.