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

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Lifetime WarrantyOn All AT3 Brand Products

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

This includes AT3 Red Dot Sights, Handguards, Iron 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.

Fast & Free Shipping On orders over $50

You will receive fast, free shipping for all orders over $50

Shipping cost is $7.99 for orders under $50. We ship with UPS or USPS, depending on the item.

Most orders received by 1pm CST ship the same day

You will receive an email with tracking information at the time of shipment. To expedite shipping, we may ship your order from multiple warehouses. Orders placed on weekends, holidays, or after 1pm will ship the following business day.

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.

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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Customer Reviews

Based on 9 reviews
Never know!!

Always like to have extra, you never know when a spring will break or fly away, nice bag of spare parts

good good

nicely packaged, does the job. repeat customer... repeat repeat repeat lol

Thanks for sharing your feedback, Charles. We're glad you're satisfied with your purchase. Cheers!
Got what I needed

Tracking is a little inaccurate but only by a few hours

Thanks for sharing your feedback, Heywood. We're glad you're satisfied with your purchase. Cheers!
Damn good idea.

I’m constantly dropping parts and the bloody things disappear into the space time continuum. Thankfully I have several F-U bags which not only make up for my clutz but also make me laugh whenever I need to grab something out of it.
Nice idea.

Thanks for sharing your feedback, Mark. We're glad you're satisfied with your purchase. Cheers!
Worked as needed

Best bang for your buck

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