Aero Precision M4E1/BA Enhanced Slip Fit Magwell (SFM™)


  • Low profile design, free of snag points, offers unobstructed manual of arms
  • Durable single piece nylon construction
  • Simplified hardware reduces potential failure points to effectively none
  • Ultralight construction: 0.50 oz including hardware

In stock


The M4E1 Slip Fit Magwell (SFM) brings “extra flare” to your Aero Precision M4E1 and Ballistic Advantage Enhanced receivers, increasing the existing funnel of the receiver by approximately 170%. The unique slip fit attachment method, co-developed with Darq Industries, offers users a simplified one piece construction with reduced points of (potential) failure – it has been proven through years of use on our EPC9, personal M4E1 builds, and Darq’s standard forged lower variants. The hardware follows this simplified approach, consisting of one 4-40 socket head screw and one threaded insert, offering a secure and reliable fit while also keeping the overall weight right at 0.50 oz.

*only compatible with Aero M4E1 and Ballistic Advantage Enhanced lower receivers. For Radian ADAC, please use this variant. For standard forged models, please use this one. If you have any trouble when installing your SFM™ please contact us for assistance. Due to the efficient attachment method, minimal torque is needed when tightening the screw. Simply tighten the screw until the split section begins to touch, then just shy of a 1/2 turn of the screw for final torquing.


PA11 Nylon Polymer

Weight w/ Hardware

~0.50 oz


– 3 in/lbs – Do not over-torque

Hardware Included

1 x Hex Screw
1 x 3/32" Allen Key


Max Length: 3.37 in / 85.59 mm
Max Width: 1.74 in / 44.19 mm
Max Height: 0.64 in / 16.25 mm

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SKU: M4E1-SFM Category: Tag:
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