2011 +3 Mag Extension Mk1

Add an additional 3 rounds to your 2011 Checkmate mags, the OEM used by Staccato, MAC, Tisas, Kimber,16rd, 17rd, and 20rd mags, and improve the ergonomics and aesthetics at the same time. 

We have designed the most intuitive to install mag extension on the market. It uses no tools, screws, clips, plates, or levers. The installation is identical to a stock base pad, simply remove the stock base pad and plastic retainer, then install our 7075 aluminum retainer and slide the new 6061 extension on. Installation and removal takes seconds and requires no tools. The assembly is rock solid, and the length stays within the 140mm tournament gauge when using a 17rd magazine tube and can also be used on 16rd mags for the C2 with stock springs. When installing on 20rd 140mm tubes purchase with the 140mm +3 spring. 

This extension can also be used on 140mm Kimber 13rd .45 magazines and adds one additional .45acp round. 

The extension features three deep v groove serrations for improved ergonomics when loading and stripping. The tool less design gives an incredibly clean look uncluttered by extra parts. We cnc engrave our logo onto the bottom of the retainer rather than the cheaper option of laser etching the anodizing.

We don't make compromises and neither should you, elevate your game with the Underworld Arms Mag Extension. 

Specifications

Not compatible with Mec-Gar/C/CS/Atlas/Prodigy mags

Adding this extension to a 20rd staccato mag may require spring tuning.

Material Base: 6061-T6 

Material Insert: 7075-T6

Weight: 1oz

Length Overall: .825"