AT3™ FU-BAG™ AR-15 Lost Parts Kit – Springs, Detents, Replacement Components

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Made an “Oops” with your New Build?  You Detent-Launchin’, Spring-Losin’ Fool, you.

We’ve all been there.  Whether it’s rolling the dice on that bargain bin LPK in your local gun shop, launching a detent across the garage, or losing a spring to the shag carpet in mom’s basement, you’re missing a part or two.  The situation is FUBAR, and you’ve F***ed Up – Building A Gun.

That’s why we’re offering the FU-BAG!  The handy bag of commonly lost lower parts, plus a couple of gas tube roll pins and an adhesive bandage.  Whatever happy little accident you’ve managed to make, we’ll help you patch it up with this bag of goodies.

Except if you jettison a detent or spring directly into your eyeball or something.  Always wear eyepro, guys.

If you need more parts for a seriously messed up situation, check out the Motherfu-Bag!  It includes more parts on the bolt that commonly break or wear out, plus spare springs and for the fire control group.

American Made Quality

  • All parts meet or exceed military specifications (Mil-Spec)
  • Components are 100% Made in the USA
  • Backed by the AT3 Lifetime Warranty

The FU-BAG Includes:

  • Bolt catch plunger
  • Bolt catch roll pin
  • Bolt catch spring
  • Buffer retainer
  • Buffer retainer spring
  • Magazine catch spring
  • Selector detent
  • Selector detent spring
  • (2) Takedown/Pivot pin detent
  • (2) Takedown/Pivot pin detent spring
  • Trigger guard roll pin
  • Mil-Spec Disconnector Spring
  • (2) Gas Tube Roll Pins
  • (1) Adhesive bandage for any other boo-boos you make

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Have Questions About this Product?

The AT3 Tactical store has a 90 day no-hassle return policy for products in good condition. You can view the full details of our return policy here.

If you encounter an issue or defect with a product after 90 days of your purchase, you can refer to the manufacturer for a warranty claim. Their policies are below.

AT3 Lifetime Warranty Logo

All AT3 Tactical Brand Products carry a lifetime warranty against manufacturer’s defects.

This includes AT3 Red Dot SightsHandguardsIron Sights, and any other product that carries the “AT3 Tactical” or “AT3™” name. For other brands (ex. Magpul or Troy), please refer to the manufacturer’s warranty policy.

In the event that your AT3™ product becomes unusable, we will repair or replace the product at no charge to you.

If we cannot repair your product, we will replace it with a product in perfect working order of equal or better physical condition. The warranty is fully transferable, but we may require information about the original purchase to validate the authenticity of the product.

If your product is in need of warranty service, please contact AT3 Tactical to start the process

Our contact info is available here. To expedite processing, please provide your order information and description of the defect.

Please note: The AT3 Lifetime Warranty does not cover loss, theft, intentional damage or cosmetic damage that doesn’t affect the performance of the product.

Customer Reviews

Based on 468 reviews
Because you made a boo-boo!

Gotta love the AT3 sense of humor!! Great product too. 👍

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.

Joseph Udulutch
Parts kit and sight

Bought the fubar parts kit to keep in my pack in case of a lost part.
Bought the leos sight with the green Lazer I have the one with the red Lazer and it works fine at night but is hard to see during the day. The green one is much easier to see during daytime. Both sights work well for me. Probably won't use the Lazer much but always nice to have for low light.

Thanks for sharing your feedback! We're glad you're satisfied with your purchase.

Marcus Gigandet
Great price fast shipping

Exactly what I needed

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Just what I needed

Replaced the parts I lost plus some and the perfect name.

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Great price, fash ship

My sons and I are having a great time building and shooting our own rifles. However we learned a noob lesson when a buffer tube detent and spring flew into the eather. This kit is exactly what was needed and for a great price. I got 2 because I know this wont be the last time it will happen. Thanks AT3!

Thanks for sharing your feedback! We're glad you're satisfied with your purchase. Cheers!