Leapers Inc. UTG Pro AR15 S4 Mil-Spec Stock Kit, Black - Complete Ops Upgrade

The Leapers Inc. UTG Pro AR15 S4 Mil-Spec Stock Kit gives you a complete drop-in stock solution built tough for real-world use. If you're running an AR-15 and need a compact, adjustable stock that won't quit—whether you're training hard, running plates in a tactical setup, or just want a rock-solid upgrade from milspec basics—this kit handles it. You get everything in the box: the stock itself, extension tube, buffer, buffer spring, receiver end plate, and castle nut. Bolt it together and get to work.

The S4 design runs 4.28" with four adjustment positions, so you can dial in length of pull that works whether you're in a shirt, chest rig, plate carrier, or heavy load-out. The matte black impact-resistant polymer is made to take abuse without breaking, and Leapers builds these with tight tolerances—no wobble, no rattle, solid lockup every time. This is mil-spec geometry, meaning it'll integrate cleanly with standard AR-15 receiver extensions and components.

Whether you're upgrading from a bare-bones mil-spec stock or building a new rifle, this kit eliminates the parts-hunting phase. Everything you need to complete your receiver tube is included and ready to install.

Key Features

• Four-position length of pull adjustment (4.28" compact length)
• Impact-resistant high-strength polymer construction
• Complete kit: stock, extension tube, buffer, spring, end plate, and castle nut included
• Mil-spec compatible with standard AR-15 platforms
• Matte black finish
• Designed for secure fit under load-bearing gear and plate carriers
• Tight tolerance engineering for minimal movement

Specifications

Frequently Asked Questions

Will this stock kit work with my AR-15?

Yes, this is a mil-spec stock kit designed for any AR-15 with a standard mil-spec receiver extension tube. The kit includes all components needed for installation.

What's included in the kit?

The complete kit contains the S4 stock, extension tube, buffer, buffer spring, receiver end plate, and castle nut. You have everything needed to assemble a functional stock assembly.

How much adjustment does the four-position design offer?

The stock features four distinct adjustment positions with a 4.28" overall length. This allows you to customize length of pull for different use cases, including shooting in body armor or load-carrying gear.

Is this stock suitable for wearing with a plate carrier or body armor?

Yes. The compact 4.28" length and four-position adjustability are specifically designed to work comfortably when wearing load-bearing vests and plate carrier systems, making it a solid choice for tactical or duty setups.