SAG MK4 S20131 5-Slot Chassis with RSB Cutout for AK
- $1 349
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In short: SAG MK4 S20131 is a five-slot chassis for AK platforms, combining the MK1 front section, an upper with integrated gas tube, an RSB cutout and the detachable rear cover architecture used by MK3.
Compatibility checkpoint
- Confirmed platform family: AK.
- Front format: five-slot MK4 configuration.
- Rear-sight provision: RSB cutout preserves the original sighting line.
- Specialist installation required: MA-136-02, MA-136C and MA-136-05.
- Model: S20131.
Selection rule: Choose S20131 for the five-slot MK4 layout with the RSB cutout. The listed MA variants require specialist installation.
Purpose
The MK4 architecture combines an MK1 handguard block with an upper section and integrated gas tube, plus a detachable rear cover derived from MK3. The forward 1913 interface stays installed during routine partial disassembly, while the detachable rear section provides an additional mounting segment.
Technical specifications
| Main chassis | High-strength aluminum alloy |
|---|---|
| Front architecture | MK1 handguard block, five-slot configuration |
| Upper section | Integrated gas tube |
| Top interfaces | Forward 1913-MIL-STD monorail plus detachable rear 1913 segment |
| Rear-sight provision | RSB cutout |
What's in the box
- MK1 handguard block × 1
- Upper with integrated gas tube × 1
- Detachable MK3-type rear cover × 1
- Required fastening components × set
Installation
Install according to the official SAG MK3/MK4 manual. MA-136-02, MA-136C and MA-136-05 configurations require a specialist workshop.
Frequently asked questions
Which platform family fits S20131?
S20131 is confirmed for compatible AK platforms.
What distinguishes the MK4 architecture?
It combines an MK1 handguard block, an upper with integrated gas tube and a detachable MK3-type rear cover.
Does this version include an RSB cutout?
Yes. S20131 is the five-slot version with an RSB cutout.
Which models require specialist installation?
MA-136-02, MA-136C and MA-136-05 require installation in a specialist workshop.
SAG Specs
General
Mounting & Rails
Kit Contents
Care & Chemicals
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