Geissele Automatics Ultra Duty AR-15 Lower Parts Kit - Black

Manufactured by Geissele Automatics
SKU: 05-435B
MPN: 05-435B
Manufactured by Geissele Automatics
3 Reviews

In Stock

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The Geissele Automatics Ultra Duty AR-15 Lower Parts Kit comes with everything you need to build out your lower receiver. However, it comes with Geissele’s selection of high-quality parts that give you a slight advantage over standard Mil-Spec parts. First, it features the Geissele Ambidextrous safety selector allowing you to manipulate your firearm from the right or left hand side. The next upgrade is the Maritime extended bolt catch that makes dropping the bolt much faster and easier. The trigger guard is machined out of aluminum and is enlarged giving you more room to use the trigger if you are wearing gloves. Additional improvements are the textured takedown pins and magazine release. The Geissele Ultra Duty AR-15 Lower Parts Kit is a great way to build out your lower receiver without having to pick every single part.

Kit Includes:
  • Maritime Bolt Catch
  • Bolt Catch Plunger
  • Bolt Catch Spring
  • Bolt Catch Roll Pin
  • Mag Release
  • Textured Billet Mag Release Button
  • Mag Release Spring
  • Buffer Retainer Spring
  • Ambidextrous Safety
  • Buffer Retainer 
  • Safety Detent Spring
  • Safety Detent 
  • Enlarged Billet Trigger Guard 
  • Trigger Guard Roll Pin
  • Takedown Detent Springs 
  • Takedown Detents 
  • Textured Takedown Pins

Geissele Automatics manufactures confidence, offering quality triggers and components for the warfighter and competitor. They were established in 2004 with the mission to build the highest quality, reliable triggers for competition and their first trigger, the Hi-Speed National Match trigger, was so popular that they were asked by the Department of Defense to produce a select-fire trigger for the United States Special Operations. Again, it was a success and Geissele decided to bring a semi-automatic version to the civilian market for law enforcement and personal protection.
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BrandGeissele Automatics
Fire Control GroupNone
California Prop 65 warning

 WARNING: This product can expose you to chemicals, which are known to the State of California to cause Cancer and Reproductive Harm. For more information go to

Ratings & Reviews

3 reviews

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Exactly what you expect

by -

Great fit and finish, all the parts you expect minus an Allen key to install the trigger guard and safety.

A upgrade


An upgrade on all the functional parts that you will be using to control your weapon. I like every piece. The only issue I had was the safety felt mushy. And after about 2 weeks of trying different springs and detents I realized the hole in my grip was a little deep. So once I put a small shim in the grip hole, the safety now functions smooth and tactile. Just adding that info in case someone has a similar experience.

Better than milspec

by -

Only had one issue mag release button was too small and a significant gap was present on both of the flat sides of the oval. Other than that really impressive all contact surfaces are knurled with a Dimond pattern. All the finishes are all nicely done with no machine marks anywhere. This will replace preferred LPK.