What is MOS? By definition the  Glock Modular Optical System (MOS) is a reliable and simple mounting  system engineered by Glock.  MOS facilitates the attachment of a reflex sight (Red Dot) onto the iconic semi-automatic pistol. Ideally, a reflex sight needs a machined platform to mount to the top of a semi-auto slide. Some systems … Continue reading The Glock Modular Optical System (MOS) ~ Simon Stewart