The B5 Systems Sierra K Extension Kit for AR15, Black is a stock accessory that fits AR15.
The Sierra K Receiver Extension Kit is the proprietary mounting system for the Sierra K Buttstock. It consists of a reduced-length, mil-spec diameter, 7075 aluminum, 5-position receiver extension, a short heavy buffer (3.5 oz), extra power spring, castle nut, and quick disconnect end plate. All parts are made of mil-spec materials and finishes and proudly Made In The USA.
Stock accessories fine-tune how a stock fits you or add parts for a stock you already own. Check the accessory is listed for your exact stock model before ordering.
How It Compares
Also compare the Sierra K Receiver Extension Stock for B5 Systems Sierra K Extension, Collapsible Precision Stock for AR-15, Short and Collapsible Precision Stock for AR-15, Medium. Browse all stocks & Chassis and the full B5 Systems range.
Ideal For
- AR-15 owners fitting the B5 Systems Sierra K buttstock
- Compact builds that need a reduced-length 5-position receiver extension
- A complete install with buffer, spring, castle nut and QD end plate included
Key Features
- Reduced-length 5-position Receiver Extension Constructed of 7075 Aluminum
Compatibility & Fitment
Fits AR15. Not sure it fits? Contact us before you order and we will check for you.
Technical Specifications
Brand | B5 Systems |
Type | Stock Accessory |
Model | Extension Kit |
Platform | AR-15 |
Color | Black |
MPN | SRK-1660 |
UPC | 814927024793 |
US Shipping & Support
Genuine B5 Systems, brand new and covered by the manufacturer's warranty. Shipping is free on US orders of $99 or more, and smaller orders ship from $6.95. Questions about fit, mounting or which option suits your setup? Our team is glad to help before and after your purchase.
Frequently Asked Questions
What does the Sierra K Extension Kit fit?
Fits AR15.
Is this a genuine B5 Systems product?
Yes. It is a new, genuine B5 Systems product sourced through an authorized US distributor.
How much is shipping?
Shipping is free on US orders of $99 or more. Orders under $99 ship at a flat rate from $6.95 to $9.95, depending on the order total.
