How to mount a Holosun 509T X2 on a Picatinny rail: it is a Holosun 509T enclosed-emitter reflex, so it takes a 509T-to-RMR adapter plate on an RMR Picatinny mount. Which mount to buy and the height to pick.

Updated 05 September 2026.

Scope Mount Finder / Every rail, tube and red-dot footprint

Fit a Holosun 509T X2 on a Picatinny rail

Name: Fit a Holosun 509T X2 on a Picatinny rail: published specification
Creator: Scope Mount Finder
License: https://creativecommons.org/licenses/by/4.0/

The Holosun 509T X2 is a Holosun 509T optic. Here is the mount that puts it on a Picatinny rail and the footprint it must match.

Needs adapterThe Holosun 509T X2 is a Holosun 509T enclosed-emitter reflex, so it reaches a Picatinny rail through its supplied 509T-to-RMR adapter plate on an RMR mount. Buy the 509T-to-RMR adapter plate on an RMR Picatinny mount, not a mount cut for any other footprint.

OpticHolosun 509T X2Holosun 509T

interface

Mount509T-to-RMR adapter plate on an RMR Picatinny mount

seats on

RailPicatinny rail (MIL-STD-1913)5.23 mm slot, 10.01 mm pitch

Fit readoutBench figures

Fitment

Optic type

enclosed-emitter reflex

Bridge

the supplied 509T-to-RMR adapter plate

Mount the Holosun 509T X2

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The Holosun 509T X2 is cut to the Holosun 509T footprint. To put it on a Picatinny rail you fit a 509T-to-RMR adapter plate on an RMR Picatinny mount: the mount carries the Holosun 509T pattern on its top and clamps the rail below, so the sight screws down to the pattern it was made for.

A mount cut for a different footprint will not take the Holosun 509T X2. Match the mount to the Holosun 509T pattern, and pick the mount height for the cowitness or heads-up hold you want on the rifle or carbine.

Related fitments

›Holosun 509T X2 footprint and mountthe optic
›Holosun 509T footprintthe pattern
›How this footprint reaches a railthe general fit
›Picatinny rail (MIL-STD-1913)the base

Questions and answers

Fit a Holosun 509T X2 on a Picatinny rail?

The Holosun 509T X2 is a Holosun 509T enclosed-emitter reflex, so it reaches a Picatinny rail through its supplied 509T-to-RMR adapter plate on an RMR mount. Buy the 509T-to-RMR adapter plate on an RMR Picatinny mount, not a mount cut for any other footprint.