Before committing to any other brand of MRDS, do yourself a favour and seriously consider the Holosun HS507C or it's titanium housing upgrade version. The standard Aluminum Housing/Body of the 507C is plenty tough, but with a larger and clearer aiming window than the (much more expensive) Trijicon RMR. The Holosun is priced at $430 CAD, making it one of the most affordable "serious duty" choices available. It comes with a full suite of advanced features such as "shake-awake" battery-conserving "sleep mode" after 5 min motionless, solar cell operation off of ambient light with battery back-up, indefinite battery life, choice of Dot, Circle, or Circle-Dot reticles, included Picatinny Mount, RMR Footprint for mounting, etc. The HS 507C is an incredibly sophisticated yet simple, durable and reliable MRDS by any standard and is an incredible bargain as well! The upgraded model with a solid Titanium Housing/Body steps the already-impressive durability up a final notch to equal or even best the legendary (and expensive) Trijicon RMR.
I am in no way affiliated with Holosun, just a very satisfied convert to their product, particularly the HS507C MRDS. I have over 20 handguns and shoulder arms equipped with MRDSs. 7x RMRs, 5x Leupold DPPs, 3x Vortex Razor and Venom, 1x Mepro, and (most recently) 6x Holosuns. Do yourself the favour of a bit of Youtube research such as Aaron Cowan of Sage Dynamics' legendary Review of the Holosun HS507C - you won't look back after that, trust me!